ABSTRACT
Background: Serum Ferritin [SF] and iron both show acute phase responses to inflammation, so iron may fall and ferritin rise independent of the marrow iron store. Bone marrow iron store has been considered the gold standard, but is invasive, painful and expensive and not suitable for everyone. Serum transferrin receptor [sTfR] which is the concentration of the soluble fragment of transferrin receptor in serum, is an important new haematological parameter. The ratio of sTfR to log SF is known as sTfR-SF index. This study was conducted to evaluate sTfR, Ferritin and sTfR-F Index in diagnosing and differentiating iron deficiency anaemia [IDA] from anaemia of chronic disease [ACD]. Methods: One hundred and sixteen [116] adult subjects [80 anaemic and 36 controls] who already had their bone marrow examination done for various reasons were included in the study. sTfR, SF, and their index were measured and compared with bone marrow iron stores. Absence of iron stores denoted IDA whereas increased macrophage iron with decreased siderocytes and sideroblasts was diagnostic of ACD. Results: Out of 80 anaemic patients, 47 were diagnosed as IDA while 33 were diagnosed as ACD. In case of IDA the diagnostic accuracy of index was 91.57%, sTfR had accuracy of 85.54% while SF had accuracy of 75.90%. In case of ACD, the diagnostic accuracy of sTfR was 91.30%, index 89.86%, while SF had accuracy of 79.71%. Conclusion: sTfR-SF index is a better parameter than sTfR or ferritin alone but should only be used when the results of these parameters seem altered or a bone marrow aspiration is mandatory for diagnosis of ACD. The estimation of sTfR or index may offer a simple non invasive method that may enable more accurate assessments of iron status in such patients. Keywords: Serum Transferrin Receptor, Index, Iron deficiency anaemia
ABSTRACT
To diagnose and differentiate iron deficiency anaemia [IDA] from anaemia of chronic disorders [ACD] using serum concentration of soluble transferrin receptors [sTfR]. 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. 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/l, whereas mean + SD sTfR levels in ACD patients was 2.96 + 1.28 mg/l, 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. 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