Screening of β-thalassaemia trait by means of red cell indices and derived formulae

Context: Thalassaemias are a group of genetic disorders with tremendous morbidity and mortality that are present widely across the globe. Aim of the Study: To evaluate the usefulness of automated haematology analyser-based red cell indices and formulae derived from these indices in β-thalassaemia trait (BTT) detection. Settings and Design: Prospective study conducted over a period of 1 year. Materials and Methods: The study included 301 cases with mild-to-moderate reduction in haemoglobin (Hb) with a lower cut-off value of 8 g/dl. Automated haematology analysis was done by using an "Arcus Diatron" (2000) for all these cases. A cut-off value of mean cell volume (MCV) < 76 fl and serum ferritin level < 12 ng/ml were taken for high-performance liquid hromatography (HPLC) screening. Based on these indices we evaluated eight automated analyser red cell indices and formulae - red blood cell count (RBCC), MCV, mean cell Hb (MCH), red cell distribution width (RDW), red cell distribution width index (RDWI), Mentzer index (MI), discriminant score (DS) and mean density of Hb per liter (MDHL) - for all 301 cases. Youden′s index was computed for all derived indices. Results : Out of 98 cases screened by HPLC (D-10 VARIANT; Bio-Rad Laboratories), 88 turned out to be positive for BTT (HbA2 > 3.5%). Indices like RDW, RDW with low MCV, MCH, RDWI and DS were found to have a better discriminating function (higher Youden′s index) compared with RBCC, MDHL and MI. Conclusion: Automated haematology analyser-based red cell indices and certain formulae derived from these indices have a high predictive value in screening BTT