Lab Values Pocket Guide For Nurses

By Rachael Jason

The need for medical practitioners to understand the importance of laboratory tests in medical decision-making cannot be overemphasized. This pocket guide is written to aid nurses and nursing students alike understand and interpret the different laboratory investigations with ease. Understanding Laboratory values aid in the diagnosis, management and monitoring the effectiveness in the treatment of disease conditions, which makes lab values an important part of the NCLEX. This book also provides the necessary information to aid nursing students to pass the NCLEX at first try. 

You will get the following information in this book:

How to obtain Lab Samples Correctly   

 Provides guide to the different Laboratory Bottles  

Hematological Tests & Values

Serum Electrolytes Tests   

Tests for Cardiac Disease   

Renal Function Tests   

Test for Liver & Gastrointestinal Function   

Arterial Blood Gas (ABG) Analysis   

Serological Tests   

Endocrine Function Tests 

Tests for Malignant Conditions (Tumor Markers)   

Body fluid & Stool Analysis   

Tests for Other Conditions and lots more   

• Language: English
• Publisher: Rachael Jason
• Release date: Jun 2, 2019
• ISBN: 9781393185598

Book preview

Chapter1

Obtaining Lab Samples Correctly

D

iagnostic lab tests are medical procedures used to determine a patient’s condition. Therefore, it is important for nurses to be knowledgeable about the different tests and their normal values to make informed clinical decisions. In this book, we will look at some common tests and lab values (reference ranges) that will serve as a guide for every nurse. Reference ranges for laboratory tests are a range of values used by health professionals to interpret a set of medical test results. If a test result is not within a given reference range, it is indicative of a patient with some abnormal conditions. Lab values are important tools for diagnosing disease conditions. Before we go into the procedures for different lab tests, let’s have an overview of common laboratory bottles and samples that are collected in each of these containers.  

Laboratory Blood Bottle Guide

Blood collection tubes are known as vacutainers because they have vacuums within. These vacuums facilitate the flow of blood during lipectomy. Vacutainers have different color tops which indicate the type of anticoagulant present in the container.

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Purple topped bottle

The purple top bottle is commonly used for the full blood count (FBC). This includes Haemoglobin (Hb) electrophoresis, platelets (PLT) and White Blood Cell Count (WBC).

The purple bottle is also used for other tests including HbA1C estimation which is important in the assessment of diabetic blood sugar control, DNA and RNA isolation. The anticoagulant present in this bottle is Ethylene Diamine Tetra Acetate (EDTA). EDTA preserves the morphology of blood cells by preventing the blood in the container from clotting. It is important to allow proper mixing of anticoagulant by the inversion of the tubes. An inversion is one complete turn of the wrist, 180 degrees, and back to 0 degrees. Each container has a specific number of inversions to be carried out to allow for thorough mixing of the anticoagulant. 

Yellow/Gold Topped Bottle

The Gold top bottle is used for a range of biochemistry test including Urea & Electrolytes (U&E). For instance, Sodium (Na), Potassium (K), Urea, and Creatinine tests used for Kidney function and electrolyte derangement assessment. Other tests that require the gold-top bottle include Liver function tests (LFT), C-reactive protein (CRP), Bone profile (Ca/Phos/Albumin/ALP), Magnesium, Lipids, Thyroid Function Tests (TFT), and Cardiac Enzymes (e.g., Troponin T). The same bottle is also used for various and more specialized endocrinology, oncology, toxicology, virology, and immunology tests.

Blue Topped Bottle

The blue-topped-bottle is for hematology tests to assess the clotting system. Coagulation screen carried out with the blue-topped-bottle include Prothrombin Time (PT), Activated Partial Thromboplastin Time (APTT), and Fibrinogen.

Trisodium citrate in liquid form is the anticoagulant used in this tube. To maintain a proper anticoagulant amount, specific ratio for different test is maintained. 200μl of trisodium citrate and 1.8ml of blood is added in the tube.

For Prothrombin time estimate, a ratio of 1:9 is used that is, 1 part of citrate (anticoagulant) and 9 part of blood is ideal. For Erythrocyte Sedimentation Rate (ESR) estimation by Westergren method, a ratio of one to 4 is used. That is 1 part of citrate and 4 part of blood.

Red Topped Tube

The red-topped tubes are of two types. The first is plain vial which has no anticoagulant but may contain clot activators, e.g. kaolin. The second type of red-topped tube contains anticoagulant.

When blood is collected in a plain vial red-topped tube, it clots. This is to allow for the separation of blood from serum. The separation of serum is enhanced by centrifuging. One important thing to note is to avoid collecting CSF sample in a clot activator vial and blood sample collected in the plain vial should not be refrigerated. Refrigeration of blood sample will lead to hemolysis. 

Grey Topped Bottle

The grey-topped bottle is used for two specific biochemistry tests:

- Blood Glucose: This can be fasting glucose or random glucose.

- Lactate: which can be raised in any condition causing tissue hypoperfusion, e.g., Sepsis or Acute Ischaemia.

Sodium fluoride and potassium oxalate are used as anticoagulants in this tube. Fluoride is an inhibitor of the glycolytic enzyme enolase and thus decrease the consumption of glucose by the cellular components of blood.

Samples collected for blood glucose estimation should be processed as soon as possible.

Green Top Bottle (Heparin Tube)

The green-topped bottle also known as Heparin tube is used for collecting samples for electrolyte estimation. The walls of the tube are coated with either lithium heparin or sodium heparin. Heparin is derived from porcine intestinal mucosa. Sodium heparin is used for electrolyte estimation because the sodium coat can only influence the result by an additional 1 – 2 mmol/L of sodium only. Heparin tubes are also used for sending blood for karyotyping.

Pink Top Bottle

The Pink-topped bottle is used to send blood samples to the transfusion lab for patients who may require a blood transfusion. Group & Save or crossmatch can be requested. Group & Save determines and stores the patient’s blood group so blood can be ordered swiftly if needed. Crossmatch refers to the process of ordering blood for the patient.

Typically, the bottle must be labeled by hand at the patient’s bedside after confirming the patient’s details.

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Blood Culture Bottles

Blood culture bottles are used to send samples to microbiology for culture, isolate causative organism, and enable targeted antimicrobial therapy. Protocol for collecting samples varies between local trust, but you may be required to fill more than one bottle. Some trust requires two samples to test between aerobic and anaerobic organisms. However, an aseptic approach is crucial to avoid contamination. 

Chapter2

Hematological Tests & Values

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H

ematology is a branch of medicine that deals with the study of blood, blood-forming organs and blood diseases. Hematology tests include laboratory assessment of blood formation and blood disorders.

Tests for Anemia

Anemia is referred to as low oxygen-carrying capacity of red blood cells. This could be as a result of reduced red blood cells or dysfunctional red blood cells. 

There are five tests in diagnosing anemia. All of these tests involve taking a sample of venous blood from a patient and transferring it into a purple-top tube. The focus when evaluating anemia is on the red blood cells. The first test is to determine what percentage of the blood is taken up by the red cells. In this test, the intact Red Blood Cells (RBC) are seperated from the plasma by centrifuging and packing them at the bottom of a capillary tube. Then the total volume of the whole sample is compared by the volume taken up by the packed down red cells. With this, you can determine the percentage of blood that is made up of red cells. This number is normally around 40% and is referred to as Hematocrit.

The second test determines the amount of hemoglobin (the main functional protein of red cells) present in the blood sample. To carry out this test;

1.  Lyse the red cells in plasma and measure the heamoglobin concentration. This test is called the Hemoglobin test and the normal value is between 13.2 -17.3g/dl (male) and 11.7 -15.5g/dl (female).

The Hematocrit and hemoglobin test are very tightly correlated. For practical purpose when one of the tests is up, down or normal, the other is up, down or normal. In anemic patients, both hematocrit and hemoglobin test values are low. As a condition, you would be given both values.

2.  The second test is not a test for anemia but gives you information on the quality of the red cells, which makes it a useful diagnostic tool for finding out why a patient is anemic. This test examines the size of the red cells. The entire packed red cells are sorted from small to big and counted up to