Evaluation of serum transferrin receptor concentration in diagnosing and differentiating iron deficiency anaemia from anaemia of chronic disorders.

OBJECTIVE To diagnose and differentiate iron deficiency anaemia (IDA) from anaemia of chronic disorders (ACD) using serum concentration of soluble transferrin receptors (sTfR). METHODS One hundred and seventy six adult anaemic patients were diagnosed on bone marrow examination as IDA and ACD in the Department of Haematology, Armed Forces Institute of Pathology, Rawalpindi from November 2001 to May 2003. They were further evaluated with sTfR, serum iron, total iron binding capacity (TIBC) and serum ferritin. These biochemical investigations were compared with results of bone marrow iron status, which served as gold standard. Absence of stainable iron in the bone marrow was diagnostic of iron deficiency, whereas abundance of iron along with decreased siderocytes and sideroblasts was considered diagnostic of ACD. Data was collected on a proforma and analysed using software SPSS (version 11.0) and t-test was used to test the statistical significance. Specificity, sensitivity positive and negative predictive value of the sTfR test was calculated. RESULTS Out of 176 patients studied, 90 (51.1%) were diagnosed as ACD whereas 86 (48.8%) as IDA. The mean +/- SD sTfR levels in IDA patients was 9.68 +/- 2.48 mg/I, whereas mean +/- SD sTfR levels in ACD patients was 2.96 +/- 1.28 mg/I, thus clearly separating the two categories of anaemic patients. Both the sensitivity and specificity of sTfR in IDA was found to be 100%, whereas in ACD, these were 66.6% and 100% respectively. The positive and negative predictive value, in case of IDA was 100%, whereas in ACD it was 100% and 74.1% respectively. The results of serum iron, TIBC and serum ferritin correlated well in IDA, with a fall in serum iron, raised TIBC and decreased serum ferritin, except in few cases in which concomitant inflammatory conditions resulted in falsely high serum ferritin level. Serum iron and TIBC were not useful in cases of ACD. However, the serum ferritin cutoff level of 90 ng/ml was evaluated which virtually excludes IDA, and found this highly effective in cases of IDA alongwith chronic inflammatory conditions. CONCLUSION The results show that in case of simple IDA, sTfR concentration is significantly raised and it has a very high test efficiency in this condition. However in case of ACD the positive predictive value is high (100%) but the negative predictive value is compromised (74.1%). It is therefore a reliable laboratory index of IDA and in distinguishing IDA from ACD).