A DXA Primer for the Practicing Clinician: A Case-Based Manual for Understanding and Interpreting Bone Densitometry

By Angelo A. Licata and Susan E. Williams

Despite public perception, osteoporosis remains a widespread, devastating disease, and a very serious and costly public health threat.   Early detection and treatment must be a priority for primary health care providers.  Dual-energy X-ray absorptiometry (DXA) is the principal x-ray technology used to diagnose osteoporosis in its early, asymptomatic stages, to assess treatment efficacy, and to guide treatment decisions. It remains the gold standard today.  A DXA Primer for the Practicing Clinician: A Case-Based Manual for Understanding and Interpreting Bone Densitometry is developed around real cases of patients’ DXA measurements.  The content is derived from presentations given by the authors at a national society training course and exemplifies not only the  complete body of education provided through these lectures but the full range of previously undiscussed nuances as well. This practical, easy-to-read title provides the day to day problems of DXA usage that new users may encounter and that training courses do not have time to provide in detail.  The central focus of the book is the presentation of what is normal and what is problematic in the use of DXA, depicting various scenarios with real case histories of patients, their corresponding DXA images and the data that explain the problems.  Unique in approach and presentation, this case-based manual will be of immense value to all practitioners -- and students – interested in providing optimal diagnosis and treatment of osteoporosis.

• Language: English
• Publisher: Springer
• Release date: Nov 20, 2013
• ISBN: 9781441913753

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Angelo A. Licata and Susan E. WilliamsA DXA Primer for the Practicing Clinician2014A Case-Based Manual for Understanding and Interpreting Bone Densitometry10.1007/978-1-4419-1375-3© Springer Science+Business Media New York 2014

Angelo A. Licata and Susan E. Williams

A DXA Primer for the Practicing ClinicianA Case-Based Manual for Understanding and Interpreting Bone Densitometry

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Angelo A. Licata

Departments of Biomedical Engineering and Endocrinology-Metabolism, Cleveland Clinic, Cleveland, Ohio, USA

Susan E. Williams

Endocrinology, Diabetes and Metabolism, The Cleveland Clinic Foundation, Cleveland, Ohio, USA

ISBN 978-1-4419-1374-6e-ISBN 978-1-4419-1375-3

Springer New York Heidelberg Dordrecht London

© Springer Science+Business Media New York 2014

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Foreword

Welcome to one of the most interesting and misunderstood clinical tools in all of medicine – clinical densitometry. Clinical densitometry, also known as DEXA or the preferred DXA (dual-energy x-ray absorptiometry) has become the gold standard in the diagnosis and treatment of primary osteoporosis and other demineralizing bone diseases for more than 20 years. Technological advances in safe and noninvasive measurements of bone density have catapulted the field of osteoporosis into prominence in clinical practice. Bone densitometry is the singular advancement in medicine which has made the diagnosis and treatment of osteoporosis possible. Through this technology, patients at high risk for fragility fractures are frequently identified in the early stages of disease, long before skeletal changes can be observed on standard x-rays. For similar reasons of sensitivity, this technology has advanced the development of various therapeutic agents for the treatment of osteoporosis because it measures significant changes in bone mass within relatively short periods of time, thereby aiding timely drug development. As a result, many new therapies for the treatment of osteoporosis are available to complement the increased awareness of disease prevalence and morbidity.

Moreover, since DXA utilizes very low levels of radiation, far less than a routine chest x-ray, for example, it is safe for patients and lowers costs for installing machinery because there is no need for special shielding in rooms housing equipment. This latter point has made DXA accessible to practitioners who can easily incorporate scanners in an ordinary office ­setting. The cost of a machine is far less prohibitive also than traditional x-ray imaging equipment and has led to its widespread use and availability in community practices and clinics. DXA machines are now found in a wide variety of clinical offices, and they are typically operated by certified radiological technologists.

Most clinical practitioners who use DXA have no training in interpreting data or reports. No formalized training existed until 1994, when the International Society for Clinical Densitometry (ISCD) established training and reporting standards to address this gap. Its courses, conducted in this and many other countries, have become an invaluable and one-of-a-kind resource for educating clinical practitioners in the basic understanding and use of DXA, and interpretation of its results. ISCD has established accredited board certification examinations for clinicians and technologists, establishing standard competencies and continuing education requirements for those who operate the machines and interpret the data. As of today, only a handful of states require certification. However, with the increasing scrutiny that government agencies are placing on competency and quality in medicine, certification of DXA professionals will undoubtedly become a nationally mandated standard. Likewise, the highly acclaimed textbooks in clinical densitometry by Dr. Sidney Bonnick have added much to this educational endeavor. Yet, these efforts fall short in educating the vast majority of physicians who employ this technology for patient care and do not know of these educational resources, or who do not need that degree of detailed knowledge. They are dependent upon the technical and clinical expertise of centers for skeletal densitometry and assume the reports submitted are accurate.

The interpretation of the measurements and the reporting of results, however, have not yet become standardized, although ISCD has written guidelines to overcome this educational deficiency. DXA-specific training is generally not enough. The experience of the interpreter (i.e., radiologist or otherwise) greatly impacts the quality of the report. All too frequently the interpreter lacks sufficient training to avoid over- or under-interpreting the data. Many of the technologists put in charge of DXA machines continue to provide images and data rife with errors, making interpretation by even the most highly trained subspecialist difficult at best. The referring physician does not have the tools to critically evaluate the interpretive report, is typically unaware of the need to carefully scrutinize the report received, has little to no training in doing this, and unknowingly can perpetuate reporting errors when treating patients. Subspecialists are often consulted to see patients with troublesome DXA reports not because of the severity of the diagnosis but ultimately because of the inaccuracies and failings of the report.

Our experiences as educators have led us to conclude that, in general, clinical practitioners fail to fully understand and appreciate the knowledge base required to correctly employ the technology in the clinical setting since they have not been exposed to any formal training. Moreover, they unquestioningly rely upon others for reliable clinical information essential for patient care. Many consultations, DXA data, and interpretive reports sent to our respective practices continue to demonstrate a lack of knowledge-based experience, understanding of the technology, and/or an awareness of what the data can and cannot reveal. More often than not, the computer print-out has simply been reformatted into a reporting form, standard phrases have been inserted regarding the T-scores, and the interpreter has signed the report without so much as a thought given to the clinical utility of the data, the images, and the historical information.

This textbook is primarily designed for clinical care givers who wish to understand what it’s all about. But we recognize a wider need and have cast a broad net with the intention of speaking to a wide range of medical professionals from well-seasoned clinicians and radiology technologists, to medical students, residents, fellows, and our allied health colleagues studying and working in direct patient care.

This book is not a manual for operating the equipment or understanding the complex physics involved in this technology as this has been covered in detail elsewhere. It does not substitute for any formalized course work of ISCD. The text offers busy health care providers who cannot attend structured courses another venue to educate themselves about how this technology works, how to properly interpret densitometry scans, identify the common pitfalls of the interpretive report, and highlight what DXA can and cannot tell us when it comes to bone health and fracture risk of the patient sitting in front of us in our office. Rather than a text meant to be read cover-to-cover, we headline each chapter with a key concept/question that our medical colleagues frequently ask us, and explain relevant issues through a case-based approach. We liberally include clinical cases to exemplify the concepts behind bone densitometry, its utility in various aspects of bone physiology, its short-comings, its applicability in patient monitoring, and some of the limitations and difficulties which arise due to misinterpreted images and inadequate interpretive reporting. This method allows the reader to glean key concepts quickly from numerous annotated figures and bulleted key concepts pertinent to the cases from the authors’ clinical practices.

We endeavored to make the concepts easy to understand and locate. We have purposely limited the technical language, physics, and mathematics, and worked diligently to encapsulate this educational resource into a user-friendly, portable text for a broad and diverse clinical audience. We have drawn upon our pedagogical approach with students of