Relationship between serum ferritin, anemia, and disease activity in acute and chronic rheumatoid arthritis.

The assessment of anemia in patients with rheumatoid arthritis may be difficult, especially when iron deficiency and the anemia of chronic disease coexist. The development of a radioimmunoassay for serum ferritin concentration has aided the detection of reduced body iron stores in uncomplicated iron deficiency, but its use is compromised in clinically active rheumatoid arthritis by the tendency of serum ferritin to behave as an acute phase reactant. In this latter role it correlated well with disease activity in the patients we studied. Followed serially, serum ferritin levels fell in patients whose disease activity improved after institution of appropriate therapy. In anemic patients with clinically inactive disease, supplemental iron was associated with a significant rise in hemoglobin when compared to untreated patients. Serum ferritin levels behaved independently of hemoglobin levels. Therefore even in clinically inactive rheumatoid arthritis, serum ferritin does not accurately reflect an iron deficiency.