71st AACC Annual Scientific Meeting

By CTI Meeting Technology

AACC is a global scientific and medical professional organization dedicated to clinical laboratory science and its application to healthcare. Our leadership in education, advocacy and collaboration helps lab professionals adapt to change and do what they do best: provide vital insight and guidance so patients get the care they need.

• Language: English
• Publisher: CTI Meeting Technology
• Release date: Jul 10, 2019
• ISBN: 9780463748671

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Biomarkers of Acute Cardiovascular Diseases

A-001

Categorizations and Distributions of Troponin T Results Before and after Switch to High-Sensitivity Troponin T (Roche Elecsys Troponin T Gen 5 STAT)

J. Guarente, J. E. Hollander, D. F. Stickle. Jefferson University Hospitals, Philadelphia, PA

Background: Our institution switched from standard troponin T (TnT, Roche Diagnostics USA) to high-sensitivity troponin T (hs-TnT, Roche Diagnostics USA, Elecsys Troponin T Gen 5 STAT) in April 2018. We examined laboratory data before and after this switch to evaluate distributions of results among different results categories (within reference interval (WRI), elevated (E), or critical (C)), and for changes in followup testing among first results among different results categories.

Methods: Data for troponin orders, for a period of 45 days before (PRE) and after (POST) the switch to hs-TnT, were retrieved from the laboratory information system. Summary statistics were examined for distributions of clinical categorization of results: PRE (WRI: <0.01 ng/mL; E: 0.01-0.1 ng/mL; C: >0.1 ng/mL); POST (WRI: <19 ng/L; E: 19-53 ng/L; C: >53 ng/L), and rates of second orders from first orders as a function of clinical categorization of first results. Data were analyzed using Excel spreadsheets.

Results: Dataset PRE was comprised of 6069 results from among 3206 patients (1.89 results/patient). Dataset POST was comprised of 6195 results from among 3004 patients (2.06 results/patient). There were changes in clinical categorizations of first results as follows: WRI: 77%(PRE), 66%(POST); E: 17%(PRE), 21%(POST); C: 6%(PRE), 12%(POST). These data represent an increase (by 11% of the total number of first results) in first results outside of the reference interval, and an increase (by 6% of the total number of first results) in critical first results. For dataset POST, first results in category of WRI included a new subcategory of WRI having quantifiable results (viz., WRI results that were above the lower limit of quantitation (LLOQ), 6 ng/L), comprising 55% of all WRI first results; for dataset PRE, first results WRI were by definition all below LLOQ (0.01 ng/mL). For dataset POST, 66% of first results received at least one follow-up troponin measurement, compared to followups for only 47% of first results for dataset PRE, a change of 19% among the total number of first results. The increase was primarily from followups from among first results in category of WRI. Among categories of first results, percentages receiving followups were as follows: WRI: 37%(PRE), 55%(POST); E: 78%(PRE), 86%(POST); C: 84%(PRE), 89%(POST). For followups among WRI(POST), the majority (71%) were from category of (WRI, >LLOQ).

Conclusions: After adoption of hs-TnT, there was an increase from 23% to 34% in the fraction of first results outside of the reference interval, with an increase from 6% to 12% in the fraction of first results categorized as critical. Among first results for hs-TnT, the majority (55%) were in a new category of (>LLOQ, WRI). There was an increase from 47% to 66% among first results receiving a followup measurement, accounted for primarily by the increase in follow-up tests ordered on first values in category of WRI. Although these data are from only the first 45 days after startup of hs-TnT, the distribution of first results categorizations are likely to be stable, whereas followup rates may well change as institutional experience with hs-TnT increases.

A-005

Study of Serum Ischemia Modified Albumin and Other Conventional Cardiac Markers in Acute Myocardial Infarction within 6 Hours of Onset of Chest Pain

S. Chhetri. Manipal College of Medical Sciences, Pokhara, Nepal

Background: The NH2-terminal of albumin gets altered leading to reduced binding of albumin with cobalt within few minutes of ischemia. This albumin altered by ischemia is called Ischemia modified albumin. Ischemia modified albumin levels can be assayed by spectrophotometric techniques. Previous studies done in other parts of the world have shown IMA to be a promising marker for the diagnosis of MI. However, studies regarding IMA from Nepal are scarce. We conducted this study to compare the diagnostic performance of IMA and other conventional biomarkers in patients with ACS presenting within six hours of onset of chest pain. Aims and Objectives: The study was undertaken to evaluate the diagnostic importance of Ischemia modified albumin in people with chest pain of suggestive of Myocardial Infarction presenting early to hospital. This study also aims to compare the diagnostic performance of IMA with conventional cardiac biomarkers. Materials and Methods: A hospital based, cross sectional, descriptive, case control study was carried out with 50 cases of chest pain and 50 healthy controls. Study was conducted after obtaining ethical clearance from institutional review committee of the hospital. All participants were enrolled in the study after obtaining informed written consent. Venous blood of cases and controls were processed in department of biochemistry, Manipal Teaching Hospital and quantitative values of IMA and other conventional biomarkers (cTnI, CK-MB, AST) were obtained. One step troponin I test was used for qualitative assessment of cTnI. Relevant clinical and demographic data were collected in a preformed proforma. Receiver Operating Curve was computed to assess diagnostic utility of various biomarkers, except for cTnI. Receiver Operating Curve could not be computed for cTnI as it was not quantitatively assessed. Statistics for tests of diagnostic utility were calculated for cTnI by 2 *2 tables. Results: The mean age of study group was 70.06 (10.11) and that of control group was 67.88 (9.96). Both groups were comparable in terms of gender distribution and history of smoking, diabetes and hypertension. Out of 50 cases 24 had presented to hospital within 6 hours. In the patients who presented early, the diagnostic performance of IMA was best (AUC= 0.801) followed by CK-MB (AUC=0.788) and AST (AUC=0.546). The ROC derived optimal cut off for IMA was 0.485 ABSU. At this cut off point sensitivity of IMA was 87.5%, specificity was 64%, PPV was 53.85% and NPV was 91.43%. In the current study, sensitivity of cTnI was 68%, specificity was 100%, PPV was 100% and NPV was 75.56%. Conclusion: IMA is a sensitive test with good NPV but a relatively modest specificity and PPV. Hence a negative IMA test seems to more helpful in ruling out the diagnosis of ACS in patients presenting with chest pain. However, a positive IMA test may not be as useful in ruling in the diagnosis of ACS. A positive cTnI test however virtually confirms the diagnosis of ACS because of its high specificity and PPV. However negative cTnI may not be as useful as negative IMA test. Both these test complement each other in assessment of ACS.

A-007

Performance Evaluation of Representative Immunoassays from the Cardiac Panel on the Alinity i System from Abbott Laboratories

C. Rudolph, K. Krishnan, J. Lee. Abbott Diagnostics Division, Abbott Park, IL

Background: Cardiovascular disease (CVD) is a broad term for a range of diseases affecting the heart and blood vessels. Abbott’s Cardiac Panel of assays and analyzers provide accurate, reliable results with rapid turnaround time, aiding clinicians in providing better patient care. The Alinity i system is part of a unified family of systems that are engineered for flexibility and efficiency. The design is based on insights from customers, resulting in a number of benefits including a smaller footprint, improved workflow, and greater throughput with up to 200 tests per hour. The Alinity i system has an increased reagent load capacity, holding up to 47 immunoassay reagents, onboard QC, clot and bubble detection ability, and a dedicated pre-treatment lane to provide consistent and reliable results.

Objective: To demonstrate the analytical performance of representative assays of the Cardiac Panel of the Alinity i system, which consists of assays that utilize Chemiluminescent Microparticle Immunoassay (CMIA) technology for the quantitative determination of analytes in human serum and/or plasma.

Methods: Key performance testing including precision, limit of quantitation (LoQ), linearity, and method comparison were evaluated per Clinical and Laboratory Standards Institute (CLSI) guidelines. The inputs to the Analytical Measuring Interval include the observed LoQ, imprecision across the range, and the linear range.

Results: The observed results for LoQ, precision, linearity, method comparison to ARCHITECT using Passing-Bablok regression, and determined Analytical Measuring Interval for representative assays in the Cardiac Panel are shown in the table below.

a Within-Laboratory (Total) variability contains within-run, between-run, and between-day variance components

Conclusion: Representative immunoassays from the Cardiac Panel utilizing CMIA technology on the Alinity i system demonstrated acceptable performance for sensitivity, precision, and linearity. Method comparison data showed excellent agreement with on-market ARCHITECT immunoassays.

A-008

Pentraxin 3 as a Marker of Inflammation and Atherosclerosis in Cholesterol-fed Rabbits

J. C. Gonzalez, L. M. Figueira, D. C. Gonzalez. Carabobo’s University, Valencia, Venezuela, Bolivarian Republic of

Background: Inflammation plays an important role during the atherosclerosis. Different studies have been carried out on the relationship between inflammatory markers and the development of atherosclerosis, suggesting their utility to identify the risk of an acute ischemic event and the detection of vulnerable plaques. Pentraxin 3 (PTX3) and C- reactive protein (CRP) are acute phase proteins that belong to pentraxin family and play an important role in inflammatory reactions such as in atherosclerosis. CRP is the most recognized marker for cardiovascular disease. The evidence indicates that PTX3 exerts an important role in modulating the cardiovascular system in humans and experimental models. In fact, PTX3 is strongly expressed in atherosclerotic arteries and its high plasma levels were found to be related with severity of coronary atherosclerosis, thus, its represents a rapid biomarker for primary local activation of innate immunity and inflammation. However, has been described that PTX3 has a protective role in atherosclerosis, since it attenuates leukocytes recruitment at the site of inflammation. Therefore, the role of PTX3 in the atherosclerosis is has not been established so far. Thus, we were prompted to evaluate the role of plasmatic PTX-3 and CRP in determining the presence and severity of atherosclerosis. Methods: New Zealand white male rabbits were randomly divided into two groups, control group (CG) and experimental group (EG), receiving standard diet (commercial rabbit food) and water. The EG rabbits were fed a cholesterol diet (1% cholesterol) for 12 weeks. Blood samples of overnight-fasted rabbits were collected on basal, sixth and twelfth weeks, and plasma concentration of lipid profile, PTX3 and high-sensitivity CRP (hsCRP) were determined. Half of the animals were sacrificed by cervical dislocation on sixth or on twelfth week, and the aortic arch and descending aorta was dissected for histological studies. Results: Our findings demonstrated that cholesterol diet induced significant increases in lipid profile. The PTX-3 and CRP levels were significantly higher in EG than CG both on 6th and 12th week (p < 0.001). Moreover, cholesterol diet induced advanced atherosclerotic lesions (types III and IV) in the aortic arch and descending aorta. Conclusion: These results support that plasmatic PTX-3 and CRP levels were associated with the presence of atherosclerosis and it may be regarded as novel early markers of atherosclerosis.

A-009

A Highly Stable Cardiac Troponin I Recombinant Protein: An Ideal Candidate as cTnI Calibrator or Quality Control Material

L. Shen¹, Q. L. Yu¹, H. P. Huang², Q. H. Jin¹, C. H. Xiao¹, M. Yan², Z. J. Deng², Y. Y. Liu², L. Peng², J. Luo², B. Hu², R. B. Zheng¹, J. Ge¹. ¹Hunan Yonghe-sun Biotechnology Co., Ltd, Changsha, China, ²Hunan Testing Insitute For Medical Devices, Changsha, China

Background: Cardiac troponin I (cTnI), a polypeptide expressed in cardiac muscles with 110 amino-acid residues, is one of the subunits in the troponin complex (TnT, TnI and TnC) bound to tropomyosin and actin on the thin filaments of striated muscle fibres. Previous studies indicated that cTnI released from cardiac tissue may undergo molecular changes, and most of cTnI molecule may exist as cTnI-cTnC complex. This leads to the notion that antibodies in analytical systems may not equally recognize cTnI forms, resulting the difficulty of cTnI assay standardization. Through the cooperation of AACC and NIST, a natural troponin C-I-T complex (SRM 2921) provided by Hytest, which is demonstrated to improve harmonization and commutability of the different cTnI assay platforms, is suggested to be used as the cTnI reference materials for further study. However, the practicability of SRM 2921 is limited due to its poor stability. Therefore, we focused on preparation of a cTnI reference material which could be used for improving the stability of cTnI calibrator or QC material.

Methods: The cTnI recombinant protein (M.W. 30.22 kDa) was designed as a C-I complex (named as ILCH), having 273 amino acid residues, which consists of full fragments of cTnI, a linker, and partial fragments of cTnC. The ILCH gene was inserted into the expression vector pET-28a, and the plasmid was transformed into E. coli BL21(DE3). The ILCH protein was expressed under condition of 1 mM IPTG for 4 hrs at 30oC and purified by affinity chromatography. The comparative stability study of ILCH with 8T62 (the raw material of SRM 2921 obtained from Hytest, Finland) was performed under the condition of thermal accelerated experiment at 42oC. In the thermal acceleration study, four concentrations of ILCH and 8T62 were prepared: 1.0 μg/L, 5.0 μg/L, 25 μg/L and 50 μg/L, respectively. The samples were then placed into an electric thermostatic drying cabinet at 42oC up to 50 days. The treated ILCH and 8T62 were then tested and evaluated by FIA at set intervals until 50 days. The ILCH were also measured by using Beckman Access2 cTnI assay.

Results: Our thermal acceleration results showed that the stability of ILCH was found much better compared with 8T62. For example, on Day 3, the degradation rate of 8T62 at 1.0 μg/L and 5.0 μg/L were 25.0%, and 25.9%, respectively. On Day 17, the degradation rate of 8T62 at 1.0 μg/L and 5.0 μg/L were 65.0%, and 61.6%, respectively. Notably, we found the degradation rate of ILCH at 1.0 μg/L and 5.0 μg/L were only 4.8% and -5.4% on day 17. Analytical values of ILCH were obtained from Beckman Access2 cTnI assay, and the values were found very close to that obtained from FIA.

Conclusion: In this study, we describe a highly stable cTnI recombinant protein, ILCH, which could be an ideal candidate of cTnI calibrator or QC material for assay standardization of cTnI on different assay platforms.

A-010

Hs Troponin I Performance Characteristics on Alinity i in Karachi, Pakistan

F. Z. Kanani, A. H. Kazmi. The Indus Hospital, Karachi, Pakistan

Background: We recently shifted from conventional troponin I (c trop I) assay to high sensitive troponin I (hs trop I) assay on Alinity i by Abbott Diagnostics. Alinity i system has recently been launched internationally, and we are amongst the first ones in Pakistan to adopt the assay on this analyzer. We aimed to perform analytical evaluation of hs trop I on two Alinity i analyzers.

Method: Precision: This was verified by running commercial controls at three different levels in five replicates for five days.

Accuracy: External proficiency sample were run and results compared to Architect group mean.

Sensitivity: Limit of Blank, Limit of Detection and Limit of Quantification were determined and compared to vendor claims.

Method comparison: 40 samples were analyzed for c trop I on Vitros Eci and hs trop I on both Alinity i analyzers across entire analytical measuring range (AMR). Verification of 99th percentile URL: Hs trop I was performed on 40 healthy male voluntary blood donors (20 on the each Alinity i). HbA1c and estimated creatinine clearance of the donors were also determined to further define normality.

Results: Precision study showed a coefficient of variation (CV) of 5.6/ 5.7, 1.4/ 2.7 and 1.1/4.1 for Alinity i 1 and 2 at low, medium and high levels. The samples were within total allowable error in the CAP proficiency testing survey when compared to Architect series, though with a negative bias. Limit of blank was 0.99 and 0.19 ng/L and limit of detection was 1.59 and 0.64 ng/L on Alinity i 1 and 2 respectively. Limit of quantification was verified to be less than 5.1 ng/L as claimed (4.4 and 3.6 ng/L).The assay demonstrated a CV of less than 6% at values corresponding to 99th percentile URL on both Alinity i. Passing Bablock between c trop I on Vitros Eci and hs trop i on the two Alinity i instruments showed a slope of 0.988 (r=0.99)and 0.921 (r=0.96), (95% CI included 1.0) with a negative intercept of 3.98 and 3.35, and no significant difference in mean concentrations. Hs trop I levels were below the gender specific cut offs in all healthy donors, being undetectable in 35 out of 40 males tested. It needs to be seen if 99th percentile URL levels are lower in our ethnic group.

Conclusion: The analytical evaluation of hs troponin Iiassay on two Alinity i analyzers was successful.

A-011

Robustness of the Troponin 0/1-h Algorithm for Early Diagnosis of Acute Myocardial Infarction when Measured on Two Different Instruments of the Same Type

A. Haushofer¹, J. Seier¹, M. Stübler², G. Lirk³, A. Ziegler⁴, E. Giannitsis⁵, B. Lindahl⁶, C. Mueller⁷. ¹Central Laboratory, Klinikum Wels-Grieskirchen, Wels, Austria, ²Central Laboratory for Molecular Diagnostics, Medical University of Graz, Graz, Austria, ³University of Applied Sciences Upper Austria, Hagenberg im Mühlkreis, Austria, ⁴Roche Diagnostics International Ltd, Rotkreuz, Switzerland, ⁵Department of Internal Medicine III, Cardiology, Angiology & Pulmonology, Heidelberg University Hospital, Heidelberg, Germany, ⁶Department of Medical Sciences and Uppsala Clinical Research Center, Uppsala University, Uppsala, Sweden, ⁷Department of Cardiology and Cardiovascular Research Institute Basel, University Hospital Basel, Basel, Switzerland

Background: Accelerated protocols for acute myocardial infarction (AMI) diagnosis, based on relatively low troponin concentrations and small acute changes of 3-5 ng/L over 1 h in blood, have been validated in several research studies. However, blood samples were typically measured on a single instrument. Therefore, evidence and guidance is required for routine operation and workflow in a centralized laboratory, where serial troponin samples from the same patient might be measured on two different instruments of the same type.

Methods: In this sub-analysis of the multicenter TRAPID-AMI study, we evaluated the performance of the accelerated 0/1-h AMI algorithm when measuring serial troponin samples from the same patient, with symptoms suggestive of AMI, on two parallel instruments. Patients eligible for inclusion provided informed consent for remeasurements and 707 samples were available. The 0-h and 1-h samples were measured with the Elecsys® Troponin T-high sensitive (cTnT-hs) assay on two different cobas 8000 analyzers (Roche Diagnostics). AMI diagnosis was determined by 0/1-h criteria for rule-out (cTnT-hs <12 ng/L and change <3 ng/L at 1 h) and 0/1-h criteria for rule-in (cTnT-hs >52 ng/L or change >5 ng/L at 1 h); remaining individuals were classified to the observation zone. Outcomes were analyzed for different data combinations, e.g. all samples measured or 0-h and 1-h samples randomly assigned, on the two different instruments.

Results: When running all samples from the same patient on two different instruments of the same type, results were in agreement for 691/707 (97.7%) samples analyzed: 354 rule-out, 88 rule-in and 249 observation zone. Results differed (instrument 1/instrument 2) for 16 (2.3%) samples: 1 observation/rule-out; 1 rule-in/observation and 14 rule-out/observation. No reclassifications from rule-in to rule-out were observed and only 1 reclassification from rule-in to observation (0.1%). The potential variation introduced by the parallel instrument setup is thus small compared with variations introduced by an instrument switch when using traditional diagnostic protocols, e.g. a single cutoff.

Conclusions: The 0/1-h algorithm appears to be safe and effective for triaging patients with suspected AMI when measured on two different instruments of the same type.

Disclaimer: The claims discussed in this abstract have not been cleared or approved by the FDA.

The aforementioned authors have developed this abstract on behalf of the TRAPID-AMI investigators.

A-012

Measurement of Novel Adipokine Visfatin in Young Patients with Acute Myocardial Infarction

D. Stejskal, R. Šigutová. University Hospital Ostrava nad Faculty of medicine Ostrava University, Ostrava-Poruba, Czech Republic

Background: Fat tissue produces a variety of secreted proteins (adipocytokines) with important roles in metabolism. Recently was isolated a newly identified adipocytokine, visfatin, that is highly enriched in the visceral fat of both humans and mice and whose expression level in plasma increases during the development of obesity. Visfatin has been also proven to be a proinflammatory mediator involved in the process of atherosclerosis. Visfatin has been shown to play a role in plaque destabilization as it is found abundantly in foam cell macrophages within unstable atherosclerotic plaques. The aim was to evaluate an assay for the determination of Visfatin in human serum, and to investigate its clinical relevance as a marker of acute myoradial infarction in young population (Men under 45y, Women under55y).

Methods: We clinically tested a sandwich ELISA assay in young individuals with acute myocardial infarction (n=50). Control population were the healthy probands without inflammation, hepatic or renal injuries, under 55 years of age

Results: Visfatin in sera can differentiate healthy subjects from young patients with acute myocardial infarction (5 vs. 27 ng/L). Visafatin in sera of AMI probands, correlated with glucose, creatinine, hsCRP and uric acid. Healthy probands had no such correlations. ROC analysis: visfatin cut off concentration was 20 ng/l with sensitivity 86% and specificity 91%. AUC of cTNI was 0.96, AUC of visfatin was 0.96, dif not differ.

Conclusion: We conclude that visfatin in serum is new independent potencial marker of AMI

A-013

Data Mining: Biological Factors Associated with Blood Cardiac Troponin I Concentration in China

D. Li¹, D. Wang², D. Wang¹, C. Ma¹, J. Wu¹, P. Li¹, X. Guo¹, L. Qiu¹. ¹Department of Clinical Laboratory, Peking Union Medical College Hospital, Peking Union Medical Colle, Beijing, China, ²Department of Obstetrics and Gynecology Peking Union Medical College Hospital, Peking Union Medical College, Chinese Academy of Medical Science, Beijing, China

Background: Cardiac troponin is the cornerstone biomarker for the diagnosis of acute myocardial infarction. The aims of this study were to evaluate the association of biological and temporal factors with plasma cardiac troponin I (cTnI) concentration in a large group of Chinese outpatients and to explore which of four factors (gender, age, time of blood sampling, and season of the year) has the biggest influence on plasma cTnI levels.

Methods: Analytical data with outpatient cTnI results were downloaded from the laboratory information system from January 1, 2012 to September 20, 2018. All cTnI levels were measured using a Siemens Dimension EXL automatic chemiluminescence immunoassay analyzer. A statistical method was used to strictly exclude outliers. A total of 86,381 outpatients were enrolled in the study.

Results: In subjects over 60 years old, cTnI levels gradually increased with age in both males and females. cTnI levels reached their highest values in subjects aged ≥ 80 years (0.030 µg/L in males and 0.027 µg/L in female). In subjects over 70 years of age, cTnI levels were significantly higher in males than in females (P < 0.05). cTnI concentrations varied in subjects with different times of blood sampling. Both in men and women, cTnI concentrations reached a maximum at 05:00 hours (0.030 µg/L and 0.026 µg/L, respectively) and peaked again at 20:00 hours (0.029 µg/L and 0.023 µg/L, respectively). Additionally, there were significant differences among the four seasons of the year (P < 0.05). In winter, cTnI levels were usually higher than those in spring. Linear regression analysis showed that the factor, age ≥g80, had the greatest impact on cTnI levels.

Conclusion: Plasma cTnI levels were significantly influenced by gender, age, time of blood sampling, and season of the year. Thus, in order to avoid incorrect identification of cTnI values as abnormal, a cTnI reference interval needs to be established, taking into consideration the gender and age of the subject, the time of day of blood sampling, and the season of the year.

A-014

Elevations of High Sensitivity Cardiac Troponin I in Athletes during a Long-Term Period of Routine Training Out of Competition

J. Diaz - Garzon¹, P. Fernandez-Calle¹, A. K. Aarsand², S. Sandberg², A. Buno¹. ¹Laboratory Medicine Department, La Paz University Hospital, Madrid, Spain, ²The Norwegian Quality Improvement of Laboratory Examinations, Haraldsplass Deaconess Hospital and Norwegian Porphyria Centre, Department of Medical Biochemistry and Pharmacology, Haukeland University Hospital, Bergen, Norway

Background: Cardiac troponin (cTnI) concentrations have been shown to increasee after high endurance exercise such as competitions in athletes and thereafter to be decreasing over the next 24-48 hours. However, the variation of cTn in athletes during long-term stable training conditions has not been studied. The aims of this study were to assess if cTn concentrations increase during stable training conditions, and if these elevations were maintained over time as well as the influence of previous exercise and the time since the last training period. Methods:

Subjects: 30 (15 males and 15 females), aged 19-53, were recruited from triathlon clubs. Inclusion criteria: absence of any physical injury; training of more than 13 hours per week; medical examination and a stress test including electrocardiogram without any abnormality (cardiovascular, kidney or other chronic diseases or any abnormal blood test results); no hospitalization during the previous 4 weeks; no pregnancy or breastfeeding within one year. Sample collection: Eleven monthly samples per subject were collected at 8-10 am under standardized pre-analytical procedures , after ten hours fasting and the avoidance of high endurance exercise the previous 24 hours and being out of competition at a minimum the previous week. Subjects filled in a questionnaire at each visit including health status, medication, last competition, last training, etc.

Sample analysis: Serum samples were measured in duplicate on an Atellica analyzer (Siemens Healthineers), using a unique reagent lot 10391012. All samples from each subject were analysed in the same analytical run. Internal quality control (BioRad. Cardiac Markers, lot 2366) was performed at three levels. High sensitivity troponin I (hs-TnI) method was chemiluminescence: LoQ 2.5ng/L; 99th percentile (p99) 38.6 ng/L for females and 53.5 ng/L for males. Statistics: Mann-Whitney and Pearson tests were performed to compare hs-cTnI values for subjects having had moderate exercise the previous 24 hours with those who had not exercised. The correlation between hc-cTnl concentration and the time since the last exercise session was examined.

Results: Interquartile range of hs-TnI concentration (ng/mL) were 12.81 (7.3-46.4) and 4.5 (2.8-20.5) for males and females respectively. Female cohorts: 17.5 % of 146 results were above the sex-specific p99, 4 out of 15 athletes (26.7%) with at least one value > p99. Male cohort: 21.6% of 146 results, were above the sex-specific p99. 6 out of 15 athletes (40%) with at least one value >p99. 7 athletes maintained values above p99 over time. There were significant differences in hs-TnI between the results of individuals who had performed moderate exercise the day before sampling (13.9 ng/mL) and the results of individuals who had rested (4.8 ng/mL) (p<0.001). There was a significant correlation between cTnI concentrations and the elapsed time since the exercise was done (Pf= - 0.196, p<0.001).

Conclusion: Hs-cTnI values above the p99 were observed in athletes under stable training conditions, and these were maintained over time. Moderate exercise 24h before the samples were drawn was directly related to hs-cTnI concentrations, and inversely related to the elapsed time since the last exercise session.

A-015

Are We Meeting the 1 Hour Turnaround Time for Cardiac Troponin Testing as Recommended by the 2018 Expert Panel?

C. S. Lau, S. P. Hoo, S. F. Yew, S. K. Phua, T. C. Aw. CHANGI GENERAL HOSPITAL, Singapore, Singapore

Background: The 2018 American Association for Clinical Chemistry and International Federation of Clinical Chemistry (IFCC) expert panel recommended that cardiac troponin (cTn) results should be reported within 60minutes from sample reception. We describe our experience with turn-around-times (TAT) for high-sensitivity (hs)-cTnT results.

Methods: We are a 1000-bed acute care general hospital with 500-600 daily attendances at the emergency department (ED). Hs-cTnT is requested through the computerized physician order entry (CPOE) system. Upon blood collection (heparin) a barcode is generated (time 1), and samples are sent to the laboratory via pneumatic tubes. In the laboratory sample details are verified (time 2) and samples placed into the Cobas8000 (Roche) lab automation system (LAS). After centrifugation and de-capping, plasma is aspirated for hs-cTnT testing (9 min assay) by electro-chemiluminescence immunoassay (Cobas e801). Results are auto-validated and transmitted to the electronic medical records (time 3). TAT from lab reception to reporting (R-R TAT = time3-time2) and collection to lab reception (C-L TAT = time2-time1) of samples from September 2018-January 2019 were analysed. MedCalcSoftwareV18.11 (Ostend, Belgium) was used for statistical analyses.

Results: Data from 31363 samples were reviewed; 29425 samples (93.8%) had R-R TAT ≤60min (table 1), with a median (IQR) of 34min (13-303). Out of 1938 cases whose R-R TAT >60min, 1212 (62.5%) cases occurred outside office hours. C-L TAT was ≤60min in 29560 (94.1%) of samples with a median (IQR) of 12min (1-1243). ED samples accounted for 16733 cases (53.4%) with a median (IQR) R-R TAT of 33min (14-163) and median (IQR) C-L TAT of 9min (1-369).

Conclusion: The laboratory is close to achieving the AACC-IFCC TAT goals for troponin testing, but gaps remain. Closer attention to after-office hour service and prompt delivery of samples to the laboratory is needed. Critical success factors include CPOE, heparin tubes, pneumatic tubes, LAS, and autovalidation.

https://files.abstractsonline.com/CTRL/9D/A/375/452/2A8/40F/7A3/FFD/EA6/443/81B/D2/g626_1.jpg

A-016

Relationship between Estimated Glomerular Filtration Rate and Serum Biomarkers of Cardiovascular Disease

L. Pang, H. Li. Peking University First Hospital, beijing, China

Background: Chronic kidney disease (CKD) is associated with an increased cardiovascular disease (CVD) mortality risk. The purpose of this study was to investigate the relationship between alterations in estimated glomerular filtration rate (eGFR) and serum biomarkers of CVD.

Methods: We examined the cross-sectional associations of eGFR and high sensitive cardiac troponin I (hs-cTnI), creatine kinase (CK), CK-MB, lactate dehydrogenase (LDH) and brain natriuretic peptide (BNP) in 812 individuals without overt CVD.

Results: There were significant differences of hs-cTnI, CK, CK-MB, LDH and BNP among eGFR < 60, 60 - 90 and ≥ 90 ml/min/1.73 m². There was a strong and significant negative correlation between eGFR and hs-cTnI, CK-MB, LDH, BNP whereas there was no significant correlation between eGFR and CK when eGFR was taken into consideration as a continuous variable. eGFR was associated with these biomarkers of CVD. For example, eGFR < 60 ml/min/1.73 m² (vs ≥ 90 ml/min/1.73 m²) was significantly associated with a [ratio (95% CI, P value)] 11.22 (5.58-22.54, P < 0.001), 3.05 (1.83-5.09, P < 0.001), and 7.84 (4.93-12.45, P < 0.001) times higher hs-cTnI, LDH and BNP, respectively. After adjustment for potential confounders, eGFR was associated with a 2.83 (1.08-7.41, P = 0.035) times higher of elevated hs-cTnI.

Conclusion: Reduced eGFR is associated with elevated hs-cTnI, LDH and BNP among individuals without clinically evident CVD.

A-017

Performance Evaluation of a New Troponin T-high Sensitive Assay with Increased Tolerance to Biotin

R. Imdahl¹, G. Albert², S. Kunzelmann³, C. Rank³, R. Zerback⁴, A. von Meyer⁵. ¹Labor Augsburg MVZ, Augsburg, Germany, ²Roche Diagnostics International Ltd, Rotkreuz, Switzerland, ³Roche Diagnostics GmbH, Penzberg, Germany, ⁴Roche Diagnostics GmbH, Mannheim, Germany, ⁵Institute for Laboratory Medicine and Microbiology, Kliniken Nordoberpfalz AG, Weiden, Germany

Background: Pending the results of ongoing clinical trials, future multiple sclerosis therapies might comprise high-dose biotin regimens (≤300 mg daily) that can produce high blood biotin concentrations, but no higher than 1200 µg/L. Biotin concentrations >20 µg/L may interfere with the existing Elecsys® Troponin T-high sensitive assay (cTnT-hs; Roche Diagnostics), which is used to measure cardiac troponin T (cTnT) to aid the diagnosis of acute myocardial infarction. In this study, we evaluated the performance of a new assay, referred to here as cTnT-hs*, which was designed to reduce biotin interference.

Methods: Assessments were performed using up to two assay applications (18 min and 9 min [STAT]) on three analyzers (cobas e 411, cobas e 601 and cobas e 801). Biotin interference with cTnT-hs* was determined by measuring recovery in a series dilution of 11 samples with biotin concentrations ranging from 0-3600 µg/L. Repeatability was evaluated in five serum sample pools (n=75 each). Method comparisons of cTnT-hs* vs cTnT-hs, cTnT-hs* 18 min vs 9 min, and cTnT-hs* on different analyzers were evaluated using Passing-Bablok regression and Pearson’s correlation. Clinical concordance of cTnT-hs* vs cTnT-hs (n=300 lithium-heparin plasma samples) was calculated. Repeatability, method comparisons and clinical concordance were tested using samples that did not contain biotin.

Results: Recovery using cTnT-hs* (cobas e 601; 18 min) was ≥99% for biotin concentrations ≤500 µg/L, ≥96% for biotin concentrations ≤1250 µg/L, ≥83% for biotin concentrations ≤2000 µg/L, and ≥12% for biotin concentrations ≤3600 µg/L. For cTnT-hs*, coefficients of variation for repeatability in serum samples (mean cTnT concentrations ranged 8.528-9768 ng/L) were: cobas e 411, 1.0-13.8% (18 min) and 1.1-11.7% (9 min); cobas e 601, 1.1-2.6% (18 min) and 0.9-2.5% (9 min); cobas e 801, 1.2-4.9% (18 min) and 1.3-3.4% (9 min). High correlation was demonstrated for all method comparisons: cTnT-hs* vs cTnT-hs using the 18 min application on cobas e 601 (y=1.003x + 0.650; r=1.000) and cobas e 801 (y=0.999x + 1.04; r=1.000); cTnT-hs* using 18 min vs 9 min applications (cobas e 601; y=0.975x + 1.22; r=1.000); and cTnT-hs* on each of the three analyzers using 18 min or 9 min applications. Clinical concordance for cTnT-hs* vs cTnT-hs (cobas e 601; 9 min) was high using the global (excluding US) 14 ng/L cutoff, with 95.3% negative and 100% positive agreement; Passing-Bablok regression, y=0.973x + 0.959 (r=1.000).

Conclusion: The new cTnT-hs* assay provides substantially greater tolerance to biotin interference, without affecting the performance of the existing cTnT-hs assay, across all platforms evaluated. cTnT-hs* could be used for patients with multiple sclerosis taking biotin up to 300 mg daily without any special precautions.

A-018

Examination of the Analytical Performance of the New High Sensitive POC Assay PATHFAST hs-cTnI

E. Spanuth¹, P. Engesser², E. Giannitsis³. ¹DIAneering Diagnostic Engineering & Research, Heidelberg, Germany, ²Mitsubishi Chemical Europe, Düsseldorf, Germany, ³Department of Medicine III, Division of Cardiology, University Hospital Heidelberg, Heidelberg, Germany

Background: The main analytical criteria for high-sensitivity cardiac troponin (cTn) assays are (i) imprecision (CV) at the 99th percentile value < 10%, (ii) detectable values above the limit of detection (LoD) in > 50% of healthy individuals, (iii) higher 99th percentile cutoffs in males than in females whereas 99th percentile cutoffs in females were significantly lower than the overall cutoff. We aimed to evaluate high sensitivity criteria for the point of care cardiac troponin I (cTnI) assays using the PATHFAST™ platform (LSI Medience Corporation, Tokyo).

Methods: Plasma samples were measured using the PATHFAST hs-cTnI. An imprecision profile was obtained by serial measurement of pooled heparin plasma samples according to Clinical & Laboratory Standards Institute (CLSI) guidelines. The limit of detection (LoD) was evaluated according to CLSI EP17 A2. The proportion of detectable values above the LoD was established by using 474 plasma samples of healthy individuals (236 women and 238 men, mean age 51 ± 14 years, range 18 - 86 years), in whom chronic diseases or cardiac disorders were excluded. The 99th percentile values were determined for all individuals, as well as women and men separately.

Results: Imprecision (CV) at the 99th percentile value were < 6%. The imprecision profile revealed the following values (mean (ng/L/CV): 1.99/21.6%; 3.13/8.35%; 8.31/6.85%; 14.67/5.13%; 19.6/5.71%; Mean cTnI values were higher in males than in females: 6.11 (24.05) ng/L in males and 4.60 (42.84) ng/L in females. LoD was established according to CLSI EP17-A2 with 2.9 ng/L. In the healthy population (N=474) detectable values (% > LoD) were overall 366 (77.2%); women 165 (69.3%); men 201 (85.2%), respectively. According to CLSI C28-A3 the following 99th percentiles were obtained: overall 27.47 ng/L, males 31.3 ng/L, females 24.9 ng/L. Only slightly higher cTnI values were found in subjects aged >65 years compared to subjects aged <65 years. The highest values in males aged >65 years were 27.40 ng/L and did not exceed the manufacturer recommended 99th percentile cutoffs of 29 ng/L).

Conclusion: In this analysis, the PATHFAST hs-cTnI POC assay fulfilled the analytical criteria for high-sensitivity cTn assays with high analytical accuracy according to the guidelines and definitions of the AACC / IFCC. Analysis of gender-specific 99th percentile values demonstrated significantly higher cutoff levels in males than in females. The imprecision slightly above the LoD at 3.13 ng/L was found to be 8.35%. Detectable values above the LoD were different between males and females (85.5 and 69.3%).

A-019

Influence of Pre-Analytical Factors on Lipoprotein Measurement by NMR

K. A. Roberts, B. C. Leindecker, R. J. Scott, L. J. Donato, A. S. Jaffe, J. W. Meeusen. Mayo Clinic, Rochester, MN

Background: Low-density (LDL-P) and high-density (HDL-P) lipoprotein particle numbers are associated with risk of cardiovascular disease. The most common clinical method for measuring LDL-P and HDL-P is nuclear magnetic resonance (NMR) spectroscopy, which measures the emitted frequency of methyl-protons in a static magnetic field following a radio frequency pulse. Heretofore, impact of pre-analytical factors had not been thoroughly described.

Objective: To assess the influence of fasting status, use of gel separator serum collection tubes, and storage conditions on lipoprotein results generated by NMR.

Method: LDL-P, HDL-P, and low-density lipoprotein cholesterol (LDL-C) were quantified using a Bruker Ascend 600 NMR (Bruker, Billerica, MA) with AXINON software (numares AG, Regensburg, Germany). Stored stability was determined by measuring sera from 10 subjects immediately following collection and at specified intervals after various storage conditions. Fasting or post-prandial effects on results were investigated by drawing serum from 10 subjects after an 8-hour fast and again 3 hours after a meal. NMR spectra were gathered from 50 residual sera collected using gel-separator tubes and compared to values collected conventionally.

Results: All samples repeated within 20% after storage: ambient 8 hours, refrigerate 7 days and frozen 14 days. Mean ±SD fasting versus non-fasting concentrations of LDL-P were 1,488±379 compared to 1,452±317 nmol/L, HDL-P 37.2±6.8 compared to 36.2±7.4 mcmol/L and LDL-C 123±33 compared to 110±27 mg/dL (all not significant). However, NMR results from two non-fasting samples could not be quantified due to an unusually large methyl-proton signal (Figure 1, top). In a separate analysis, 96% of spectra obtained from gel separator tubes could not be quantified due to a small but predictable peak overlaying the methyl-proton signal (Figure 1, bottom).

Conclusion: While NMR spectroscopy is a powerful tool, interferences should be carefully considered. Samples from fasting subjects using non-gel tubes produce the most reliable results for measuring lipoproteins.

https://files.abstractsonline.com/CTRL/E0/6/D72/A0A/8EF/4DD/DBB/A43/59A/85F/90C/78/g691_1.jpg

A-020

Implementing High - Sensitivity Cardiac Troponin T: The Issue of Hemolysis Interference

N. Y. Tang¹, Z. Mei², K. T. J. Yeo¹, X. M. R. van Wijk¹. ¹Section of Clinical Chemistry, Department of Pathology, Pritizker School of Medicine, The University of Chicagoty of Chicago, Chicago, IL, ²Department of Pathology, Pritizker School of Medicine, The University of Chicago, Chicago, IL

Background: Cardiac troponin T (cTnT) is one of the most sensitive and specific biomarkers of myocardial injury and acute myocardial infarction. However, hemolysis causes significant interference in the Roche Elecsys Troponin T Gen 5 STAT immunoassay. According to the Roche’s package insert, a hemoglobin concentration > 0.1 g/dL (i.e. an H-index > 100 mg/dL) will lead to falsely depressed results. In our institution, 7.8% of specimens from the Emergency Department (ED) have an H-index > 100. Additionally, consecutive sample rejections were not uncommon. We thus performed hemolysis interference studies that would potentially allow us to increase the H-index limit and reduce sample rejection rate. Literature studies showed that enzymes, including cathepsin E, μ-calpain and thrombin could proteolyze cTnT. It has also been suggested that hemoglobin plays a role in mediating the negative interference. We aim to: (1) delineate a full hemolysis interferograph, (2) study the effect of protease inhibitors in hemolysate-affected samples and (3) determine the interference effect of hemoglobin alone.

Methods: Hemolysate was prepared using lysed heparinized O-negative blood. The hemolysate was mixed with a plasma pool with known cTnT concentration to create samples with H-indices ranging from 0-1600, followed by the measurement of cTnT in duplicates.To study the effect of protease inhibitors, a plasma pool with known cTnT concentration (~20 ng/L) was prepared and increasing amounts of hemolysate was added to create a hemolysate set. cTnT concentrations in hemolyzed plasma samples with the addition of protease inhibitors were compared to those in the absence of protease inhibitors. To determine to what extent hemoglobin per se contributes to the interference, plasma + hemolysate and plasma + hemoglobin specimens with hemoglobin concentrations of 0, 100, 300, 500, 700 and 900 mg/dL were prepared and the respective cTnT concentrations were compared.

Results: We found acceptable interference up to an H-index of 150, i.e. <10% depression of the cTnT result, which reduced our sample rejection rate from 7.8% to 4.1%. For samples with an H-index of 400, adding halt protease inhibitor 3 times more than the manufacturer suggested amount (concentration 3X) could keep the recovery within +/- 10%. However, since this 3X concentration caused precipitation in plasma samples, it was unclear whether the precipitate has caused artifacts in the cTnT assay. Comparing the negative interference caused by hemolysate versus hemoglobin, hemoglobin alone contributed to at least 60% of the hemolysate interference when its concentration was ≥300 mg/dL. In addition, the extent of interference contributed by hemoglobin increased at higher hemoglobin concentrations.

Conclusion: Our interference studies allowed us to significantly reduce (47%) the ED sample rejection rate. Our result showed that hemolysis interference in the cTnT assay was mediated predominantly by the presence of hemoglobin, although proteolysis may also play a role. Ongoing studies will address whether hemoglobin removal could mitigate the hemolysis interference issue.

A-021

Validation of a NGS Pan Panel for Cardiomyopathies

F. S. V. Malta¹, R. L. M. Guedes¹, A. L. Júnior², D. Zauli¹. ¹Hermes Pardini Institute (Research & Development Division), Belo Horizonte, Brazil, ²Hermes Pardini Institute, Belo Horizonte, Brazil

Background: Genetic markers have recently gained interest from physicians as they are dictating new peculiarities in cardiology, renovating tests applicability and the practical conducts. Advances in biotechnology have made available a variety of products and research possibilities on cardiomyopathies, resulting in a multitude of alternatives for doctors, patients and laboratories. Cardiomyopathies can be classified into five main groups with diverse clinical manifestations: I: Hypertrophic; II: Dilated; III: Left ventricle non-compaction; IV: Restrictive and V: Arrhythmogenic cardiomyopathy. They are characterized by complex molecular mechanisms, such as genetic heterogeneity, variable expressiveness, incomplete penetrance, multifactorial inheritance, digenic/oligogenic mechanisms, extensive genes and phenotype overlapping, which transform the genetic testing into a complex task, demanding multidisciplinary effort. Objective: Design and validate a Pan Panel for cardiomyopathies for clinical usage. Methodology: Ion AmpliSeq Designer was used to develop a Next Generation Sequencing (NGS) custom panel containing 47 genes focused in the distinct clinical presentations: I: Hypertrophic Cardiomyopathy (27 genes); II: Dilated Cardiomyopathy + left ventricular non-compaction cardiomyopathy (30 genes); III: Arrhythmogenic cardiomyopathy (12 genes); IV: left ventricular non-compaction cardiomyopathy (10 genes); V: Restrictive cardiomyopathy (8 genes) and VI: Global cardiomyopathy panel (47 genes, taking into consideration overlapping phenotypes). Control samples NA12878 and NA19240 of the Genetic Testing Reference Materials Coordination Program (GeT-RM) were obtained from Institute Coriell and sequenced in Ion S5™ platform and variant calling was performed by TVC plugin using Ion Server. Results were compared with variants retrieved from NCBI GeT-RM database. Results and Discussion: The panel presented an average of 95.5% of covered regions over 30X; however, the uncovered region represents approximately 11 kb due to the large panel size. The repeatability and reproducibility had low variability coefficients of 2.9% and 4.24%, respectively. The analytical sensitivity and specificity was 97.79% (CI: 95.26-99.19%) and 100% (CI: 100-100%), respectively. Conclusions: Uniformity inconsistency is a well-known NGS concern. The panel achieved a satisfactory performance and it can be applied into clinical practice, given that complementary sequencing should be considered for relevant uncovered regions. Clinically diagnosed patients with distinct cardiomyopathies will be sequenced for further evaluation.

A-022

Improved Low-End Precision of High-Sensitivity Troponin T (HS-TNT) on the Roche E801 Immunoassay System

C. S. Lau, S. P. Hoo, S. F. Yew, S. K. Phua, T. C. Aw. CHANGI GENERAL HOSPITAL, Singapore, Singapore

Background: The use of low values of high-sensitivity troponin T (hs-TnT) to rule out Acute Myocardial Infarction (AMI) in chest pain subjects is gaining traction. However, precision at these levels will be critical. We examined the precision of the Roche hs-TnT on the newly available immunoassay platform E801 (in use since August 2018) compared to the E601 (used from 2010-July 2018).

Methods: The Roche hs-TnT is an electro-chemiluminescence assay on the Cobas8000 total laboratory automation system. The quoted limit of detection (LoD) for hs-TnT on the CobasE601 is 5ng/L (package insert); the lowest mean hs-TnT concentration we verified (n=20) was 4.5+0.005ng/L with a coefficient of variation (CV) of 11.5% (95% confidence interval – CI: 8.7-16.8). We adopted 5ng/L as the hs-TnT LoD for E601. The lowest concentration reported on the Cobas E601 and E801 systems is 3ng/L. The imprecision of hs-TnT on the E801 was evaluated with pooled serum samples over a range of measured hs-TnT concentrations.

Results: The CV of hs-TnT on the E801 was much lower compared to the E601 (Table 1); at hs-TnT of 3.31ng/L a CV of 7.7% (95% CI: 7.2-8.2) was achieved. The LoD adopted for the E801 was 3ng/L. To corroborate the improved low-end sensitivity of the E801 hs-TnT we reviewed all hs-cTnT values of samples tested from August 2017 to January 2018 (Group A – E601) and from August 2018 to January 2019 (Group B – E801). The percentage of cases reported as below the LoD in Group A was 11.1% (4612/41501) whereas in Group B was 8.6% (3283/38145).

Conclusion: The precision and percentage of detectable hs-TnT on the E801 has improved over the E601. This will aid physicians in ruling out AMI in patients with chest pain. Besides, improved precision will be a boon in cardiac risk stratification when hs-TnT is used in community screening.

https://files.abstractsonline.com/CTRL/39/F/1CE/64D/43F/486/0A1/E5F/37C/90F/F22/42/g811_1.jpg

A-023

Validation of ESC 0/1-h and 0/3-h Algorithm for NSTEMI in Chinese Patients Attending Emergency Department

Y. Lin. Beijing Key Laboratory for Molecular Diagnostics of Cardiovascular Diseases, State Key Laboratory of, Beijing, China

Background: Acute myocardial infarction (AMI) is a leading cause of morbidity and mortality worldwide. Use of high sensitivity cardiac troponin (hs-cTn) assay can improve the early diagnosis of AMI, especially non-ST-elevation myocardial infarction (NSTEMI). Current European Society of Cardiology (ESC) guidelines recommend 0-/1-hour and 0-/3-hour ‘Rule-in’ and ‘rule-out’ algorithms for NSTEMI by using hs-cTn. However, it lacks Chinese population data based on such diagnosis process. Thus, this study is to validate 1-hour and 3-hours diagnostic strategy using hs-cTnI (ARCHITECT) in Chinese patients with suspected NSTEMI.

Methods: From January to December in 2017, 580 patients with suspected ACS presenting to the emergency department were included. Patients aged 18-75 years without STEMI, major operation within 4 weeks, severe renal insufficiency (Ccr <30 ml/min), acute myocarditis or chronic heart failure. Serial measures of hs-TnI level were performed at 0 hour, 1 hour and 3 hours in patients with suspected AMI. The diagnosis of each enrolled patient will be made according to routine clinical approach and 1-hour and 3-hours clinical approach, respectively. The routine clinical diagnosis will be made by cardiologist panel according to third universal definition of myocardial infraction through reviewing all available medical records. The NSTEMI diagnosis depended on hs-cTnI(Architect) assessment will be made a senior cardiologist according to 1-hour and 3-hours clinical approach recommended by 2015 ESC guidelines for the management of NSTEMI. Finally, the positive predictive value (PPV), negative predictive value (NPV), sensitivity, specificity and a likelihood ratio(LR) are evaluated by using 0-/1-hour and 0-/3 hours algorithm. Statistical analyses were undertaken using MedCalc software version 15.2.2 (MedCalc Software, Mariakerke, Belgium).

Results: The age of the study population was 61.63±11.04 years; 156 patients (26.9%) were diagnosed with NSTEMI, and 197 patients(34.0%) and 227 patients(39.1%) were diagnosed non-ACS and unstable angina, respectively. According to ESC 0/1-h algorithm, 171 patients(40.1%) were diagnosed with NSTEMI.

The PPV, NPV and LR of 0/1-h algorithm were 85.4%, 99.6% and 0.01. The sensitivity and specificity was 99.3% and 91.0% for 1-hour algorithm. When ESC 0/3-h algorithm using a uniform and a sex-specific 99th centile diagnostic threshold were employed, 154(26.78%) and 151(26.26%) patients were classified as having NSTEMI. In uniform threshold approach, the PPV is 92.0%, the NPV is 97.4%, the sensitivity is 95.2%, and the specificity is 95.7%. Similarly, in sex-specific threshold approach, the PPV is 91.2%, the NPV is 96.0%, the sensitivity is 92.4%, and the specificity is 95.3%.

Conclusion: In emergency departments, all Chinese patients with chest pain of suspected ACS can be rapidly, safely and effectively classified into NSTEMI, non-ACS and unstable angina depending on ESC 0/1-h and 0/3-h Algorithm with hs-cTnI.

Keywords: High-Sensitivity Cardiac Troponin I, NSTEMI, Chinese Population

A-024

Utilisation of High Sensitivity Troponin in Routine Clinical Practice

P. O. Collinson, K. Hutt. St George’s Hospital, London, United Kingdom

Objective: To assess routine ordering patterns for high sensitivity troponin requests in a University teaching hospital in a retrospective audit. The requesting protocol for troponins is based on the European Society of Cardiology (ESC) guidelines and incorporated into the Hospital Policy Guidelines document.

Methods: All troponin results coded from the Emergency Department (ED) for October 2018 where extracted from the laboratory information system. A list of patients attending plus attendance dates was then forwarded to the audit office and a corresponding list of matches plus clinically assigned diagnoses at presentation extracted from the ED information system. Diagnoses were then grouped into clinical categories based on organ system with cardiac cases subdivided according to likely clinical investigation categories.

Results: A total of 2839 requests were identified from 2394 patients, 1184 male (49.5%) median age 61.6 years (range 4.4-118.8) interquartile range (IQR) 42.1-78.1. The median number of troponin requests per patient was 1 (Range 1-5) IQR 1-1. 1656 had a single troponin ordered of which 1197 were below the 99th percentile (14 ng/L) and 449 below the LOD (3 ng/L)

Clinical diagnoses to match requests were available on 1219/2394 (50.9%) 572 males (46.9%) median age 64.6 years (range 13.9-118.7) IQR 45.0-79.4. The diagnosis subset had the same sex distribution but was significantly older (p = 0.02). Distribution of diagnosis is shown in the figure below.

Reviewing the request patterns for patients with chest pain (n = 187) 96 (51.3%) had a single troponin measured of which 45/96 (46.9%) were <3 ng/L allowing exclusion on admission. Of the remaining patients who had only a single troponin measured 42 had a troponin between 3 and 14 ng/L and 9 >= 14 ng/L.

Conclusion: There is widespread abuse of current requesting guidelines.

https://files.abstractsonline.com/CTRL/E0/A/DDD/9F0/A74/42B/1AC/9E7/FB0/3FE/163/04/g847_1.jpg

A-025

False Positive Elevation of Cardiac Troponin T Associated with Autoimmune Skeletal Muscle Injury

P. O. Collinson, P. Kiely. St George’s Hospital, London, United Kingdom

Presentation: A female Asian age 65 years was referred for statin intolerance.

Past medical history: Type II diabetes mellitus (past 8 years) and had triple vessel coronary artery bypass grafting (2011) treated with atorvastatin 40 mg daily. When she attended the clinic she reported developing severe weakness whilst on holiday such that she could not get out of a car.

Medication at first consultation: Metformin 500mg bd, Zafirlukast 20mg od, Vitamin D3 (Cholecalciferol) 1000 units daily, Clopidogrel 75mg od, Omeprazole 20mg od, Losartan 50mg od, Ezetimibe 10 mg od, Tiotropium inhaler 18µg, Spiro base inhaler.

Investigations: All measurements were performed on a Roche Diagnostics Cobas system (Roche Diagnostics) except Cardiac Troponin I (cTnI, Architect, Abbott Diagnostics LOD 1.1 ng/L, 10% CV 4.7 ng/L,) . Noted to have elevated creatine kinase (CK) total 25-OH Vitamin D of 60 nmol/L. Cardiac Troponin T (cTnT) measured with a high sensitivity assay (LOD 3 ng/L, 10% CV13 ng/L) was elevated but no cardiac symptoms. Her serial results are shown in the table below.

Genetic testing (next-generation sequencing) excluded familial hypercholesterolemia with intermediate risk of polygenic hypercholesterolemia and the Rs4149056 genotype T/C (SLCOB1 gene, intermediate risk of myositis). A rheumatologist confirmed the diagnosis of myositis and performed an anti-muscle autoantibody screen, negative for typical anti-muscle antibodies but positive for an antibody to HMGCoA reductase. Her symptoms resolved with statin cessation with a fall in CK

The elevated cTnT with cTnI within the reference interval excluded myocardial injury. Polyethylene precipitation excluded a macrotroponin causing cTnT elevation. cTnT fell in parallel with CK. She was not rechallenged with a statin. Elevation of cTnT but not cTnI has been reported in conditions with muscle damage and muscle regeneration.

Conclusion: Auto immune myositis secondary to statin therapy with skeletal muscle regeneration and re-expression of a cross reacting TnT isoform.

A-026

A Baseline Novel High Sensitivity Cardiac Troponin I Level below the Limit of Quantitation Rules Out Acute Myocardial Infarction in the Emergency Department

B. Cook, J. McCord, M. Moyer, G. Jacobsen, R. Nowak. Henry Ford Hospital, Detroit, MI

Background: Cardiac troponin (cTn) measurements are used for the diagnosis of acute myocardial infarction (AMI). High sensitivity cTn assays allow for very early rule out of AMI, leading to more rapid diagnostic decision making. The objective of our study was to determine the utility of a baseline high sensitivity cardiac troponin (hs-cTnI) value (Access hsTnI, Beckman Coulter; Brea, California) below the limit of quantitation (LOQ) to rule out AMI in patients presenting to the Emergency Department (ED) with any suspicious symptoms of a cardiac etiology.

Methods: This was an observational trial enrolling subjects presenting to the Henry Ford Hospital (HFH) ED (Detroit, Michigan) with symptoms suspicious for AMI. Informed consent was obtained and an ED physician clinically evaluated subjects by history, physical examination, ECG, blood testing (including hospital cTnI), and chest x-ray as appropriate. Blood specimens were collected within one hour after a triage ECG was obtained (within 10 minutes of presentation). Frozen plasma specimens (<80 degree C) were thawed once and hs-cTnI was measured using the Beckman Coulter Access 2 system in the clinical laboratory at HFH. Cardiac troponin I was measured using the Access hsTnI assay per manufacturer’s instructions. Analytic performance testing for hs-TnI in HFH patients established a total imprecision (%CV) of 4.5% (26 ng/L), 6.2% (833.8 ng/L), and 6.0% (6605.8 ng/L). The Beckman Coulter published LOD (equals LoQ at 20% CV) and LoQ at 10% CV are 2.0 and 4.1 ng/L, respectively. The diagnosis of AMI was adjudicated by two cardiologists using the Third Universal Definition and Roche Diagnostics (Indianapolis, IN) Elecsys Troponin T Generation 5 assay on a Roche cobas e601 system with all available clinical data 30 days after presentation.

Results: 575 subjects were enrolled in the study with 567 having all data required for data analyses. AMI was diagnosed in 46 (8.1%) patients. 104 (18.3%) individuals had presentation hs-cTnI results <2.0 ng/L and 236 (41.6%) had values <4.1 ng/L. None of the patients with baseline hs-cTnI <2.0 ng/L had an AMI, yielding a negative predictive value (NPV) of 100.0% (CI 96.5 to 100.0%) and a sensitivity of 100% (CI 92.3 to 100.0%). Additionally, a presentation hs-cTnI value of <4.1 ng/L yielded a NPV of 100.0% (CI 98.4 to 100.0%), a sensitivity of 100.0% (CI 92.3 to 100.0%), and a good prognosis (no AMIs or cardiac-related deaths at 30 days).

Conclusions: In this single center ED study, a baseline presenting novel hs-cTnI value of <2.0 or <4.1 ng/L effectively ruled out AMI in 18.3% and 41.6% of all patients presenting to the ED and having any symptoms suspicious for AMI. Importantly all patients, not only those with chest pain, and those having symptoms for any duration or those with end stage renal disease and on dialysis were included. Additional studies are needed to validate our single baseline value

A-027

Urine Derived Renal Cells as Tools to Diagnose Salt Sensitivity

K. A. Sarpong, R. A. Felder, J. J. Gildea. University of Virginia School of Medicine, charlottesville, VA

Background: The dietary sodium recommendation by the Institute of Medicine is intended as a ‘one size fits all’ recommendation, but it is becoming clear that each individual is genetically programmed with a ‘personal index of salt sensitivity’. 25% of Americans are affected with salt sensitivity of blood pressure independent of blood pressure that results in significant increases in cardiovascular morbidity and mortality. Although the most reliable method to measure salt sensitivity is blood pressure responses to changes in dietary salt, low compliance with salt restricted diets reduces the effectiveness of this approach. We are validating a cell-based assay that utilizes dopamine 1 receptor (D1R) recruitment to the plasma membrane of living renal proximal tubule cells excreted into the urine to differentially determine the salt index of individuals.

Method: Individuals were categorized into two phenotypes, salt-sensitive and salt-resistant, as defined by a greater than 7 mm change in blood pressure in response to controlled randomized sodium intake of low (10 mmol/day) to high (300 mmol/day) sodium (Na+). Renal proximal tubule Cells (RPTCs) were semi-purified (>95% purity) from study participants’ urine samples by removing casts, cuboidal epithelial cells, and other contaminants utilizing a multi-step sieving procedure. Intracellular sodium-induced recruitment of the D1R from cytosol to the plasma membrane was measured using a selective D1R antibody. The enhancement of fluorescent signal (D1R recruitment) upon salt challenge directly correlates with an individual’s personal salt index, which is a better measurement than the arbitrary designation of salt sensitive, salt resistant, and inverse salt sensitive. We are using rigorous validation diagnostic assay tools (sensitivity, specificity, limit of detection, linearity, accuracy, imprecision) to accurately measure salt sensitivity in all study participants.

Results: Increasing intracellular Na+ resulted in a reduced D1R recruitment to the plasma membrane in salt sensitive individuals as compared to salt resistant individuals. Furthermore, there was a linear relationship between each participant’s personal blood pressure response to a change in their sodium diet ((y = −0.0107x + 0.68 relative fluorescent units (RFU), R² = 0.88, N = 12, P value = 0.0001) and angiotensin II-stimulated intracellular Ca++ (y = −0.0016x + 0.0336, R² = 0.7112, P value = 0.001, N = 10) concentration over baseline. Studies are ongoing in additional volunteers who are participating in salt sensitivity studies http://saltstudy.com. We are also developing and have published additional novel diagnostic tests for salt sensitivity involving micro RNAs.

Conclusions: Isolating RPTCs from urine provides a personalized cell-based diagnostic test of salt sensitivity index that offers advantages over a 2-week controlled diet with respect to cost and patient compliance. Furthermore, the linear relationship between the change in Mean Arterial Pressure and response to Na+ regulatory pathways suggests that an individual’s RPTC response to intracellular Na+ is personalized and predictive. Our validated cell-based D1R recruitment assay will be useful in the diagnosis of salt sensitivity in an apparently healthy normotensive adult population.

A-028

Novel Neprilysin-Derived BNP Fragments in the Plasma of Heart Failure Patients Suggest Possible Insights for a Guided ARNi Therapy

E. E. Feygina¹, A. B. Postnikov¹, N. N. Tamm², M. N. Bloshchitsyna², O. V. Antipova², A. G. Katrukha¹, A. G. Semenov¹. ¹HyTest Ltd., Turku, Finland, ²Moscow State University, Moscow, Russian Federation

Background: Entresto™ - angiotensin receptor neprilysin inhibitor (ARNi) - is a novel heart failure (HF) therapy. It comprises the inhibitor of neprilysin (NEP) - a protease that is responsible for the degradation of a variety of vasoactive substances. Among other substrates A-type and B-type natriuretic peptides (ANP and BNP) are of particular importance. The augmentation of active ANP and BNP levels is considered to be a possible mechanism of cardiac function improvement by ARNi. One might suggest