Discordance Between Hip and Spine Bone Mineral Density Measurement Using DXA: Prevalence and Risk Factors

Background: Diagnostic discordance for osteoporosis is the presence of different categories of T-scores in 2 skeletal sites of an individual patient, filling into 2 different diagnostic categories identified by the World Health Organization classification system. Objectives: To evaluate the prevalence and risk factors for T-score discordance between spine and total hip measurement sites. Methods: Demographic data, anthropometric measurements and risk factors for osteoporosis were derived from a database of 3479 patients referred to a community-based outpatient osteoporosis testing center. Dual-energy x-ray absorptiometry (DXA) was performed on L1-L4 lumbar spine and total hips for all cases. Minor discordance was defined as present when the difference between 2 sites was no more than 1 World Health Organization diagnostic class. Major discordance was present when I site is osteoporotic and the other is normal. Subjects with incomplete data were excluded. Results: In 3479 participants (2871 women; mean age, 55.7 +/- 11.9 years), concordance of T-scores, minor discordance, and major discordance were seen In 54, 42, and 4%, respectively. In multivariate logistic regression analysis, age, menopause, and obesity were identified as risk factors against T-score discordance. Conclusion: Densitometrists and clinicians should expect that at least 4 of every 10 patients tested by DXA to demonstrate T-score discordance between spine and total hip measurement sires. T-score discordance can occur for a variety of reasons related to physiologic and pathologic patient factors is well as the performance or analysis of DXA itself. (C) 2009 Elsevier Inc. All rights reserved. Semin Arthritis Rheum 38:467-471