SERUM TRANSFERRIN RECEPTOR LEVELS IN ANEMIC PATIENTS WITH RHEUMATOID-ARTHRITIS

The value of s-Transferrin Receptor (s-TfR) measurements in recognizing simultaneous iron deficiency in anaemia of chronic disease was examined in 35 anaemic patients with active rheumatoid arthritis. Based on a quantification of stainable bone marrow (marrow iron grade 0-4) and serum ferritin concentrations (levels < 60mug l-1) compatible with iron deficiency) the anaemia was found to be aggravated by iron deficiency in 19/35 or 54% of the patients. There was no significant difference between the mean s-TfR concentrations in patients with adequate iron in comparison to patients with iron depletion [2.9 (1.6) mg l-1 v. 2.7 (1.4) mg l-1; t = 0.273; p = 0.786; Student's t-test]. Mean s-TfR levels in both patients with adequate iron and depleted iron stores were within the normal range, but tended to be higher than in normal individuals [mean (SD): 1.54 (0.43) mg l-1]. In patients with no stainable marrow iron (MIG 0; N = 15) a significant inverse correlation was found between s-TfR concentrations and s-ferritin levels (r = 0. 57; p < 0.05). 5/15 patients with MIG = 0 exhibited significantly raised concentrations of s-TfR values > 3.05 mg l-1 (the highest normal value of the normal range). Increases of s-TfR levels were consistently moderate, and never exceeded a level of 7 mg l-1, which is markedly lower than concentrations measured in patients with iron deficiency anaemia. In contrast to serum ferritin, serum TfR levels were clearly shown not to be influenced by the activity of inflammatory disease, as evaluated both by ESR levels and serum concentrations of CRP. Thus the increase in s-TfR in iron deficient patients with active RA seems primarily to be a reflection of an iron deprived erythropoiesis. The measurement of s-TfR promises to possess a considerable discriminative power not only in distinguishing between the anaemia of chronic disease and iron deficiency, but also by allowing the identification of iron depletion and functional iron deficiency in patients with an anaemia of chronic disease accompanying an active inflammatory process.