PS1299 SOLUBLE TRANSFERRIN RECEPTOR AND ITS FERRITIN INDEX IN COMPARISON WITH BIOCHEMICAL AND HEMATOLOGICAL PARAMETERS FOR THE DIFFERENTIATION OF ANEMIA STATES AND CORRELATION WITH IV IRON RESPONSE

Background: Soluble transferrin receptor (sTfR) increases in iron deficiency (ID), and is used as biomarker of tissue ID and bone marrow demand for iron. Iron‐deficient erythropoiesis is the most common cause of elevated sTfR. The sTfR is not significantly influenced by infection or inflammation and appears a useful marker in the differentiation of iron states in anemia. The sTfR/log 10 ferritin index (sTfR/logFerr) is directly proportional to the measurement of the functional and storage iron compartments and seems to fully assess body iron status. Hematological indices of hypochromia indicate impaired hemoglobin synthesis due to restricted iron delivery to erythrocyte precursors. Iron restriction to erythropoiesis is a common mechanism in iron deficiency anemia (IDA) and iron sequestration accompanying to some extent anemia of inflammation and chronic diseases (AICD). In combination with sTfR, hematological indices and other parameters of ID could provide evidence of increased bone marrow iron demand and iron‐restricted erythropoiesis (IRE), that may benefit from iv iron treatment, and help to avoid unnecessary iron therapy. Aims: The aim of this study was to assess correlation between sTfR and biochemical markers of iron status and hematological indices in patients with anemia states and low serum iron, referred to our Clinic for treatment, and to investigate the association of baseline sTfR and sTfR/logFerr index with iron response. Methods: Patients over 18 years were prospectively recruited and after clinical history and examination, blood tests including hematological indices and biochemical markers were performed. Diagnostic investigations and iv iron supplementation were prescribed as appropriate. Patients were classified as: iron deficiency anemia (IDA), anemia of inflammation and chronic disease (AICD), or the combined state of IRE with AICD (IRE/AICD) using clinical findings, traditional biochemical parameters and red cell indices. To determine the iron response, the full blood count was repeated at 7 and 14 days. Serum concentration of sTfR was measured via chemiluminescent immunoassay (Access1 sTfR immunoassay system, Beckman Coulter), a new routine parameter in our laboratory, and sTfR/logFerr index was calculated. Results: The sTfR immunoassay proved a good analytical reliability. The characteristics of the patients classified in the 3 types of anaemia are shown in a table. Numbers are given as median (10–90 percentiles). Soluble transferrin receptor concentrations and sTfR/logFerr correlated significantly with mean corpuscular hemoglobin (MCH). Level of sTfR was more than 2.1 mg/l (ULN) in 32 of 35 patients with IDA, in 12 of 16 patients with IRE/AICD, and in 7 of 30 patients with AICD. Calculated sTfR/logFerr was more than 2 in 31 of 35 patients with IDA and only in 3 of 16 patients with IRE/AICD and 1 patient with AICD. There were moderate correlations between sTfR and other anemia parameters (Hb, MCV, CHr, transferrin, TSAT), but low linear association with serum ferritin and no association with CRP was found. From 57 patients treated with iv iron, 37 responded (increase of Hb>10 g/l by 2 weeks) and 20 failed to achieve an adequate increase of hemoglobin. There was correlation between iron response and sTfR and sTfR/logFerr index. Summary/Conclusion: A negative strong correlation exists between sTfR and MCH. The majority of patients had impaired hemoglobin synthesis and correspondingly high sTfR concentrations. The increased sTfR and sTfR/logFerr index correlated with subsequent iv iron response in the anemic patients and may provide help in their therapeutic management.