Reliability of Different RBC Indices and Formulas in Discriminating between β-Thalassemia Minor and other Microcytic Hypochromic Cases

Objective: Different indices and formulas of CBC parameters have been suggested as indicators of early stage screenings to detect couples with beta-thalassemia minor (BTMi). In this study, we evaluated the accuracy of five previous published formulas and compared them to our new formula (vertical bar 80-MCV vertical bar x vertical bar 27-MCH vertical bar) in screening of beta-thalassemia. Methods: All couples in the premarital beta-thalassemia screening program of Roodbar, Iran, for whom molecular analysis had been done, were selected during two years. The red blood cell parameters were applied to each formula, and a ROC curve was plotted for each one to check its discriminative effectiveness in beta-thalassemia detection. Result: None of the studied indices and formulas demonstrated 100% precision. However, we found that the Shine-Lal formula and our formula had the highest sensitivity in identifying BTMi individuals. The highest specificity belonged to our formula and Sirdah formula. Conclusion: Previous studies reported different sensitivities and specificities for the formulas. This can be attributed to different kinds of HBB gene mutations in various populations. Undoubtedly, physicians in different areas should evaluate the accuracy of published formulas for their own populations in the discrimination of BTMi from other causes of microcytic hypochromic anemia.