Serum ferritin and the assessment of iron deficiency in rheumatoid arthritis.

In order to evaluate the diagnostic and pathogenetic importance of s-ferritin and p-lactoferrin in the anemia of rheumatoid arthritis (RA), 38 patients were examined. Twenty-one out of 38 randomly selected anemic patients with classical or definite RA had iron deficiency, as estimated from the iron content in stained bone marrow aspiration. S-ferritin concentrations below 60 micrograms per litre had sensitivity and a specificity for iron deficiency of 86% and 88%, respectively, which was much better than such commonly used variables as s-iron, p-transferrin, MCV, and MCHC. Although this cut-off level is higher than in patients without inflammatory disease, s-ferritin was not correlated to disease activity. In 7 out of 8 patients, the s-ferritin level rose during iron therapy. P-lactoferrin values were within the normal range and did not vary with the anemia or with disease activity. Thus p-lactoferrin appears to be of no pathogenetic importance in the anemia of RA.