Sehgal index: A new index and its comparison with other complete blood count-based indices for screening of beta thalassemia trait in a tertiary care hospital.

Abstract

Beta thalassemia trait (BTT) must be differentiated from iron deficiency anemia to avoid unnecessary iron therapy and for the prevention of thalassemia major by genetic counseling. In a tertiary care hospital, it is vital that the screening tool is not only sensitive but also specific so as to be cost effective and save time. The aim of this study was to evaluate the new Sehgal index and compare it to existing complete blood count-based indices for the best combination of sensitivity and specificity to predict BTT. Study was done in 2 phases - Phase 1: A retrospective analysis of 1022 consecutive high-performance liquid chromatography (HPLC) cases from July 2008 to June 2011. Phase 2: A prospective analysis of 973 consecutive HPLC cases from July 1, 2011 to June 10, 2013 was done to confirm the results of Phase 1 and the applicability of the new Sehgal index. Prevalence of BTT was 28.8% (294/1022) and 25.39% (247/973) in Phase 1 and Phase 2, respectively. Receiver operating characteristic-area under the curve and Youden index was highest for new Sehgal index, followed by Mentzers index <14. The prospective study shows results similar to those in Phase 1 confirming the superiority of the above two indices. Sehgal index and Mentzers index <14 showed the best combination of sensitivity and specificity in predicting BTT. The best indices or combination can be used as a "validated flag rule" in the analyzer middleware program in a hospital for identifying suspected cases of BTT.