Evaluation of the Diagnostic Accuracy of Twelve Discrimination Indices for Differentiating β-thalassemia Trait from Iron Deficiency Anemia

The two most frequently encountered microcytic and hypochromic anemias are iron deficiency anemia (IDA) and β-thalassemia trait (βTT) need expensive laboratory tests to differentiate. Several mathematical formulae have been proposed for differentiation of these two entities, based on red blood cell indices generated by electronic cell counters. The diagnostic reliability of the twelve discrimination indices (RBC, MCV, RDW, RDW index, Mentter index, England & Fraser index, Srivastava & Bevington index, Shine & Lal index, Green & King index, Ricerca index, Ehsani index and Sirdah index) was assessed. One hundred twenty four (124) children aged between 4.0 and 17.3 years were enrolled in this study, out of which, 53 cases were β-thalassemia trait and 71 were iron deficient. The receiver operative characteristic (ROC) curve was constructed for each index to calculate the area under the curve (AUC), in addition, sensitivity, specificity, and likelihood ratios were calculated. None of the above mentioned discrimination indices found to be 100% sensitive and specific, though some of these indices (RDW, MCV, S&LI) showed more than 80% sensitivity, but their specificity for the detection of IDA was not satisfactory. EI and G&KI showed largest AUC (0.773 and 0.771 respectively) with both sensitivity and specificity above 70%. It was concluded that EI and G&KI could be used as a screening tool for differentiation of these two conditions.