In the newborn the diagnosis of alpha thalassaemia trait is easier because of the presence of haemoglobin Bart's (Hb Bart's). Alpha thalassaemia is common in Southeast Asia. Malaysians are composed of the ethnic groups Malays, Chinese, Indians and Eurasians. Hb Bart's itself is not a simple inherited character but arises from genetically determined imbalance in the biosynthesis of alpha and non alpha chains. 58% of the cord blood samples tested showed raised levels of Hb Bart's. In the Chinese the most common cause of hereditary haemolytic anaemia is haemoglobin H and hydrops foetalis is seen. The rare occurrence of these syndromes in the Malays and Indians in spite of the presence of Hb Bart's indicates an altered expression of the alpha thalassaemia gene in these populations.
This prospective study was performed to quantify glucose-6-phosphate dehydrogenase (G6PD) enzyme activity in deficient males and female heterozygotes. The methods used in the study were the fluorescent spot test, G6PD enzyme electrophoresis on cellulose acetate and quantitative assays. Forty-seven children who had been detected as spot screen deficient at birth were rescreened. Their first degree relatives were also included in the study. The mean enzyme activity of deficient males was 0.74 iu/g Hb (s.d. +/- 0.8), of female heterozygotes was 6.5 iu/g Hb (s.d. +/- 3.2) and of normal males was 12.1 iu/g Hb (s.d. +/- 3.5). The mean activity in deficient males was 6.1% of normal males. Most (35 of 47) of these fell into class 2 in Beutler's classification of G6PD variants. This indicates a population which may be susceptible to favism. Female heterozygotes had an intermediate enzyme activity with a wide scatter. Using a cut off point of enzyme activity of below 9.0 iu/g Hb gave sensitivity and specificity of 87% and 84% in detecting female heterozygotes. This group could be defined more accurately by combining quantitative assays with family studies.