[Serum ferritin as an indicator for iron substitution in patients with chronic polyarthritis].

20 patients with rheumatoid arthritis were treated with oral iron for 6 months and hematological parameters including serum ferritin levels and iron absorption were studied. 13 patients (group 1) had iron deficiency as estimated by low serum ferritin concentration (less than or equal to 30 micrograms/l); the other 7 patients (group 2) revealed normal ferritin levels. After treatment with oral iron, patients of group 1 show a significant increase in serum ferritin, serum iron, hematocrit, erythrocytes, and hemoglobin, a significant decrease in transferrin, and diminished iron absorption. In contrast, in group 2 there was no change in the above-mentioned parameters. The evaluation of iron stores by serum ferritin levels is limited to patients with inactive rheumatoid arthritis. Patients with active disease show hyperferritinemia which no longer represents the iron stores. In this case patients with active rheumatoid arthritis and iron deficiency could reveal normal serum ferritin values.