How to Interpret Dual Energy X-Ray Absorptiometry for Clinicians

Abstract

Introduction: Dual energy X-ray absorptiometry (DXA) is a clinically proven method for measuring bone mineral density (BMD) in the lumbar spine, hip, femoral neck, and forearm. It is used for management and to monitor response of therapy of metabolic bone disease. Vertebral fracture assessment (VFA) is additional software that can be added to most DXA machines for the sole purpose of evaluating of occult fractures. DXA has excellent reproducibility, and emits low radiation dose (effective dose 1–3 mSv), which is equivalent to day-to-day background radiation. International Society for Clinical Densitometry (ISCD) recommends obtaining BMD of the posterolateral L1–L4, total hip, femoral neck, and distal one-third forearm.1 It is important for clinicians managing patients for metabolic bone disease to be able to review their own DXA images and reports to ensure the accuracy of the technical performance and interpretation. This is because DXA errors are not uncommon. One particular study of 354 DXA images reviewed showed 90% contained technical errors and 80% interpretation errors were found.2 ISCD has established guidelines for the best practice in DXA performance.3 Periodic quality assurance of DXA equipments should be performed by each center. Although most centers are knowledgeable, there still remains a gap in knowledge that affects interpretation. The aim of this video is to give a short review for clinicians on how to interpret BMD on their own and recognize pitfalls that can result in error in clinical decision making. Methods: A concise review of DXA images and reports is discussed. Results: A four-step approach on how clinicians can interpret their own DXA scan images is described in the video. The first step is to evaluate for proper positioning, review of edges placement, exclude artifacts such as lesions and calcifications if present, and confirm appropriate region-of-interest placement. By applying these four steps, clinicians can reduce potential errors that can lead to errors in medical management. In addition, clinical examples are given on how to monitor BMD changes overtime. This will require each institution to establish its margin of technical error known as precision error to determine its least significant change of each site (spine, total hip, femoral neck, and distal forearm). This allows clinicians to determine whether the change noted is clinically significant. The indications and interpretation of VFA are discussed.4 This is a lateral spine imaging to evaluate for fractures. This nicely augments DXA readings in those patients who are candidates for this VFA based on ISCD guidelines, which is discussed in this video. Conclusion: There are several quality measures needed to produce quality DXA images and reports. As clinicians, we should be empowered to be able to review our own DXA images and make appropriate clinical decisions regarding treatment. No competing financial interests exist. Runtime of video: 12 mins 52 secs