Evaluation of Twenty Four Discriminant Indices for Differentiating Beta-Thalassemia Trait from Iron Deficiency Anemia in Egyptians

Background: Many Red Blood Cell (RBC) indices have been developed based on mathematical formulae to discriminate beta-thalassemia trait (βTT) from iron deficiency anemia (IDA). The latter two conditions represent the most common causes of microcytic hypochromic anemia in Egypt. This study aimed To evaluate the diagnostic reliability of 24 published discriminant indices for differentiating βTT from IDA in Egyptians. Materials and Methods: A cross sectional study included a total of 166 subjects (108 IDA & 58 βTT) aged 1-18 years were recruited from Hematology laboratory of  Pediatric Hospital, Ain Shams University, Cairo, Egypt. A full diagnostic algorithm was performed using complete blood count, hemoglobin electrophoresis by High Performance Liquid Chromatography (HPLC), iron profile and PCR detection of 22 mutations common for βTT. Twenty-four formulas were applied and their performance characteristics were calculated for each index. Results: The highest accuracy (True positive + True negative/ All cases) & Youden's Index (Sensitivity+Specificity-100) were for Red Cell Distribution Width (RDWI) and Hameed index closely followed by Keikhaei index while the least performance was for RDW-SD, RDW-CV and Shine & Lal indices. Conclusion The superiority of an index over another in distinguishing βTT from IDA allowed only partially better selection of cases warranting further confirmatory molecular studies. None of the studied formulae provided a surrogate test for Hb electrophoresis as mass screening.