Discordance in bone mineral density between lumbar spine and hip in patients with rheumatoid arthritis: A cross-sectional study

Objectives Osteoporosis is a common comorbidity in patients with rheumatoid arthritis (RA). In this study, we investigated the discordance in T-scores between the lumbar spine and hip in patients with RA. Methods This cross-sectional study included 520 patients with RA with T-scores for the lumbar spine, total hip, and femoral neck. T-score discordance was defined as differences in the WHO T-score categories between the spine and femur. Major discordance indicated osteoporosis at one site and a normal T-score at the other, whereas minor discordance represented a one-category difference. Discordance was also defined as a ≥1.5 difference in T-scores between the two sites. Results A comparison of the major, minor, and no discordance groups regarding T-scores of the lumbar spine and hip identified significant variables, including age (P < 0.001), body mass index (P = 0.008), duration of RA (P = 0.001), Health Assessment Questionnaire Disability Index (P < 0.001), pharmacotherapy for osteoporosis (P < 0.001), scoliosis (P = 0.006), and vertebral fracture (P = 0.030). Analysis of the presence or absence of a discordance ≥1.5 in T-scores between the lumbar spine and hip, showed that age (P = 0.010), sex (P < 0.001), duration of RA (P = 0.033), and type 2 diabetes mellitus (P = 0.034) were associated with discordance. Conclusions This study identified factors associated with discordance in bone mineral density between the lumbar spine and hip in patients with RA, highlighting the need for careful interpretation of site-specific measurements, particularly in high-risk patients.