Objective: Serum samples taken before the onset of RA suggest that one of the first features of RA is BMD loss. We determined the ability of radiographic BMD loss to predict RA development and arthritis persistency in patients with early undifferentiated arthritis (UA).
Methods: Five hundred and seventeen patients with early UA, included in the Leiden Early Arthritis Clinic, were assessed. Of these, 101 had hand radiographs made at first visit as well as after 6 months. BMD loss was measured using digital X-ray radiogrammetry (DXR) online. The outcome measures fulfilled the 1987 ACR criteria for RA after 1 year and arthritis persistency during a mean follow-up of 7 years. Additionally, it was assessed whether BMD measurements improved predictions compared with a validated prediction rule.
Results: A total of 53.8% of UA patients developed RA and 67.5% had persistent disease after 7 years follow-up. Highly elevated BMD loss (≥2.5 mg/cm2/month) was present in 16.3% of patients and associated with RA development [odds ratio (OR) 6.1, 95% CI 1.2, 29.2, positive predictive value (PPV) 85%, negative predictive value (NPV) 52%, sensitivity 26%, specificity 95%]. BMD loss may have an independent effect of anti-CCP when tested in a logistic regression analysis (OR 4.1, 95% CI 0.8, 21.2), although the CI is large. All UA patients that were unclassified with the prediction rule and had highly elevated BMD loss progressed to RA. BMD loss was not significantly associated with arthritis persistency (HR = 0.56, 95% CI 0.14, 2.29).
Conclusion: Present data suggest that BMD loss predicts RA development. These findings need to be verified in larger studies.