ABSTRACT
Background: Mild microcytic hypochromic anaemias due to iron deficiency (IDA) and beta thalassemia trait(β-TT) continue to be a cause of significant burden to the society, particularly in the poorer developing countries. The objective of the present study was to study the RBC based indices in patients of marked anisopoikilocytosis in determining the etiology of it, to standardize few automated red cell parameters, and also objective grading of RBC morphology on peripheral smear and interpreting its utility in indicating a diagnosis. Also, to establish a relation between value of RBC indices with that of degree of anisocytosis.Methods: A total of 500 patients diagnosed with mild microcytic hypochromic anaemia on complete blood count and peripheral blood film were included in the study. Hb, RBC count, MCV, MCH and RDW obtained from the electronic cell counter were used to calculate discrimination indices by various mathematical formulae. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and Youden’s index (YI) were calculated.Results: Green and King index demonstrated the lowest sensitivity of 70.51%. Mentzer index demonstrated the highest specificity of 96.80%. The highest and lowest PPV were found for Mentzer index (97.09%) and Sehgal index (92.81%) respectively. Sehgal’s index demonstrated the highest NPV of 95.96% and lowest NPV was exhibited by G and K (87.9%). The highest and the lowest values for Youden’s index were shown by Sehgal’s index (87.82%) and G and K index (68.47%).Conclusions: Sehgal’s index followed by Mentzer index are highly sensitive and reasonably specific in differentiating β-TT from IDA and none of the indices is 100% sensitive and specific. Though HbA2 estimation is the gold standard for diagnosing β-TT, in developing countries, Sehgal index followed by Mentzer et al, index can be used to screen mild microcytic hypochromic anaemia cases to eliminate as many false positive cases as possible to reduce the financial cost.
ABSTRACT
Introduction: Beta thalassemia trait (BTT) must be differentiated from iron defi ciency 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 specifi c so as to be cost effective and save time. Aim: 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 specifi city to predict BTT. Materials and Methods: 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 confi rm the results of Phase 1 and the applicability of the new Sehgal index. Results: 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 confi rming the superiority of the above two indices. Conclusion: Sehgal index and Mentzers index <14 showed the best combination of sensitivity and specifi city in predicting BTT. The best indices or combination can be used as a “validated fl ag rule” in the analyzer middleware program in a hospital for identifying suspected cases of BTT.