Aims: To investigate whether in Malaysia, a mean corpuscular volume (MCV) less than 80 fl and a mean corpuscular haemoglobin (MCH) less than 27 pg will identify carriers in pregnant women with severe forms of thalassaemia, a-thal 1 (a0) and classical b (b0)-thalassaemia. The results from this study will aid the implementation of a national program to screen for thalassaemia.
Methods: For classical b (b0)-thalassaemia, blood samples collected in EDTA from 153 pregnant women were taken for full blood counts and haemoglobin subtyping by automated blood counting and high performance liquid chromatography (HPLC) respectively. For a-thal 1 (a0), the full blood counts were obtained from archives of 30 pregnant women who were genotyped positive for the a-thal 1 (a0) during prenatal diagnosis for Hb Barts hydrops fetalis. The effects of storage on MCV, MCH and Hb A2 were determined by tests done daily for 3 weeks.
Results: By correlating red cell indices with high performance liquid chromatography and genotypic data, we show that mean corpuscular volume (MCV) <80 fl and mean corpuscular haemoglobin <27pg is able to detect all heterozygous carriers of a-thal 1 (a0) and classical b (b0)-thalassaemia. On storage, the MCV of heterozygous carriers with classical b (b0)-thalassaemia rose at 1% a day after 24 hours reaching a mean of 80 fl by day 15. However, the MCH and Hb A2 were stable for 3 weeks.
Conclusion: A mean corpuscular volume (MCV) <80 fl and mean corpuscular haemoglobin <27pg should be recommended as cut-off values for screening of carriers of a-thal 1 (a0) and classical b (b0)-thalassaemia. In blood samples, not processed within a day, MCH with a cut-off value of 27 pg is the recommended choice for screening of carriers. Keywords: Screen, thalassaemia, pregnant, MCV, MCH