Discordance Between Hip and Spine Bone Mineral Density Measurement Using DXA: Prevalence and Risk Factors A. Mounach, MD,* D.A. Mouinga Abayi, MD,* M. Ghazi, MD,* I. Ghozlani, MD,* A. Nouijai, MD,* L. Achemlal, MD,* ,† A. Bezza, MD,* ,† and A. El Maghraoui, MD* ,† Background: Diagnostic discordance for osteoporosis is the presence of different categories of T-scores in 2 skeletal sites of an individual patient, falling 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 osteo- porosis 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 discor- dance was present when 1 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 sites. T-score discordance can occur for a variety of reasons related to physiologic and pathologic patient factors as well as the performance or analysis of DXA itself. © 2008 Elsevier Inc. All rights reserved. Semin Arthritis Rheum xx:xxx Keywords: osteoporosis, bone mineral density, dual energy x-ray absorptiometry (DXA), concordance B one mineral density (BMD) assessed by dual-en- ergy x-ray absorptiometry (DXA) is used to diag- nose osteoporosis, assess fracture risk (1), and monitor changes in BMD over time. DXA has many ad- vantages: short scan times, quick setup of patients, low radiation dose, and good measurement precision. The World Health Organization (WHO) has proposed a set of operational criteria to define osteoporosis in postmeno- pausal white women (2). Bone measurements are ex- pressed as T-scores, which are the difference between the patients measurements and a mean value for a young adult population and divided by the young adult standard deviation. The International Society for Clinical Densi- tometry has recommended that BMD should be mea- sured for the purpose of diagnosing osteoporosis at 2 pre- ferred skeletal sites, the hip and lumbar spine. A third site (33% or one-third of the radius of the nondominant fore- arm) should be investigated if technical problems arise at any of these 2 primary sites. The International Society for Clinical Densitometry recommended also that osteopo- rosis be diagnosed on the basis of the lowest T-score for BMD found at the spine, total hip, and femoral neck (3). Actually, 1 of the reasons for measuring BMD in several sites is the presence of discordance, which can affect the diagnosis and therapeutic plan in an individual person. Discordance in diagnosis of osteoporosis is defined as the presence of different categories of T-scores (osteopo- *Rheumatology and Physical Rehabilitation Department, Military Hospital Moham- med V, Rabat, Morocco. †Professor of Rheumatology. Address reprint requests to: A. El Maghraoui, MD, Rheumatology and Physical Rehabilitation Department, Military Hospital Mohammed V, PO Box 1018, Rabat, Morocco. E-mail: aelmaghraoui@gmail.com. 1 0049-0172/08/$-see front matter © 2008 Elsevier Inc. All rights reserved. doi:10.1016/j.semarthrit.2008.04.001 ARTICLE IN PRESS