To evaluate the relationship between hemoglobin concentration and physical disability in patients with rheumatoid arthritis (RA).
Data were derived from 2495 patients with RA enrolled in 3 clinical trials (ATTRACT, ASPIRE, and START) and treated with infliximab (3 to 10 mg/kg) plus methotrexate (MTX), or MTX plus placebo. The association of hemoglobin and the Health Assessment Questionnaire (HAQ) score was assessed at baseline (n = 2471) and Week 22 (n = 2458) by Spearman correlation, and multivariate linear regression models were employed to control for confounding effects from demographic and other clinical variables. A logistic regression model was used to estimate the odds ratio (OR) for a clinically meaningful improvement (> or = 0.25 point increase) in HAQ associated with a > or = 1 g/dl improvement in hemoglobin from baseline at Week 22.
About 37% of patients with RA had anemia based on World Health Organization criteria: hemoglobin < 12 g/dl in women (39%) and < 13 g/dl in men (32%). Low hemoglobin level was significantly associated with more severe physical disability at baseline (p < 0.001), and both male and female patients with anemia had more severe disability at baseline. Improvement in hemoglobin after treatment at Week 22 was an independent contributor to improvement in HAQ, and a > or = 1 g/dl improvement in hemoglobin after treatment was associated with a clinically meaningful improvement in the HAQ score at Week 22 (OR 1.43, 95% CI 1.10-1.86; p < 0.01).
Anemia is one of the independent factors contributing to physical disability in patients with RA. Improvement in anemia following effective RA treatment may play an independent role in improving physical function.