Objective: Treatments are now available that can improve the anemia of chronic illnesses such as rheumatoid arthritis (RA). Despite recognition that anemia is common in RA and that renal function may be impaired and affect hemoglobin levels, there are almost no quantitative comparative data regarding the prevalence of anemia or decreased renal function in RA.
Methods: We studied a prospectively acquired clinical database of 2,120 patients with RA who had 26,221 hemoglobin determinations, and a control population of 7,124 patients with noninflammatory rheumatic disorders (NIRD) who had 12,086 determinations.
Results: Using the World Health Organization definition, anemia occurred in 31.5% of patients with RA, and followed a U-shaped distribution that had minimal prevalence around 60 years of age. Anemia prevalence in men was 30.4% and in women 32.0%. Anemia occurred in 11.1% at hemoglobin < 11 g/dl and 3.4% at hemoglobin < 10 g/dl. After erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) was the strongest predictor of anemia, followed by estimated creatinine clearance. Adjusted for age and sex, estimated creatinine clearance was 9.8 (95% CI 7.5 to 12.1) ml/min lower in patients with RA than in those with NIRD.
Conclusion: Anemia occurs in 31.5% of RA patients, 3 times the rate in the general population. However, severe chronic anemia (hemoglobin < 10 g/dl) is rare (3.4%). In addition, renal function is impaired in patients with RA compared with NIRD. Renal function has a small effect on the anemia of RA, and ESR and CRP have slightly greater effects.