The utility of red cell discriminant function (DF) in screening for trait

Abstract

Objective: This study was conducted to determine the frequency of minor in adult males at a tertiary referral center by using discriminant function (DF) and to compare mean MCV (mean corpuscular volume) and mean RBC (red blood cell) count in minor and non thalassaemia minor group. Study Design: This was an observational cross-sectional study. Place and Duration of Study: This study was conducted at the Clinical Laboratory, Agha Khan University Hospital from 151 August 2003 to 31st October 2003. Materials and Methods: Blood samples were taken from normal individuals in EDTA and were run on Coulter STKS. The indices that were taken into consideration were haemoglobin, RBC count and MCV. DF was calculated by formula as proposed by England and Fraser. Discriminant Function = MCV- (5xHaemoglobin)-RBC-3.4. If the value was less than zero, it was interpreted as suspected thalassaemia minor. Mean MCV and mean RBC count in thalassemia minor and iron deficiency anaemia were calculated and compared. Results: A total of 1270 individuals were included in the study. In 70 individuals, the red cell indices were found to be low. Their DF was calculated and thalassaemia minor was suspected in 49 individuals and this was confirmed with haemoglobin electrophoresis in 25 patients. Mean MCV was almost the same in both thalassaemia minor and iron deficiency anaemia. However, mean RBC count was relatively higher in case of thalassaemia minor. Conclusion: Discriminant function can be a good screening tool for evaluating patients with low red cell indices. However, further confirmation with haemoglobin electrophoresis is required for labeling a patient as having thalassaemia minor