To determine if metacarpal bone mineral density (mBMD) gain occurs in patients with rheumatoid arthritis (RA). If mBMD loss is driven by inflammation, we expect to find mBMD gain in patients who are in remission.
mBMD was measured by digital x-ray radiogrammetry in consecutive radiographs of 145 patients with RA with either continuous high disease activity (HDA; Disease Activity Score [DAS] >2.4), low disease activity (LDA; 1.6 ≥ DAS ≤ 2.4), or continuous clinical remission (CR; DAS <1.6) during a 1-year observation period. The association of mBMD changes with disease activity was investigated with multinomial regression analysis. Next, clinical variables associated with mBMD gain were identified.
Mean change in mBMD in CR patients was -0.03%, compared to -3.13% and -2.03% in HDA and LDA patients, respectively (overall, P < 0.001). Of the patients in CR, 32% had mBMD loss (less than or equal to -4.6 mg/cm2/year), compared to 62% and 66% of the patients with HDA or LDA, respectively, whereas 26% of the patients in CR had mBMD gain (≥4.6 mg/cm2/year), compared to 2% of the patients with HDA and 5% of the patients with LDA. Patients in CR had a higher chance of having mBMD gain, compared with LDA and HDA (relative risk [RR] 14.9, 95% confidence interval [95% CI] 3.0-18.7 and RR 4.7, 95% CI 1.2-6.3, respectively). CR, hormone replacement therapy, and lower age were significant independent predictors of mBMD gain.
In RA, mBMD gain occurs primarily in patients in continuous (≥1 year) CR and rarely in patients with continuous HDA or LDA. This suggests that mBMD loss is driven by inflammation.