Screening of antenatal patients in a multiethnic community for beta thalassaemia trait.

An investigation of the reliability of screening tests for beta thalassaemia trait in pregnant women was carried out as part of a programme to predict beta thalassaemia major in the fetus. Women with a mean corpuscular volume (MCV) of less than 83fl were examined further, and the reliability of various red cell indices as screening tests was assessed and compared. Over three years 696 women were found to be microcytic and were investigated further. If no abnormal haemoglobin was found by cellulose acetate electrophoresis at alkaline pH, haemoglobin A2 estimation was performed. Beta thalassaemia trait was diagnosed in 56 (8%) of the microcytic women. Both the MCV and the mean corpuscular haemoglobin (MCH) were found to be suitable screening tests for detecting patients who required further investigation. Women found to have beta thalassaemia trait or a functionally equivalent disorder were of varied ethnic origins. Of 58 such women, partners were investigated in 45 instances, and three pregnancies at risk of beta thalassaemia major were identified. Investigations for beta thalassaemia trait should preferably be carried out before pregnancy but for those already pregnant investigation should be carried out, irrespective of whether the patient seems to be iron deficient. It is advisable that partners of women with beta thalassaemia trait have hemoglobin electrophoresis, whatever their red cell indices, as double heterozygosity for either haemoglobin S or haemoglobin E and beta thalassaemia may produce severe disease.