Beta thalassaemia in Nigeria: myth or fact?

The high prevalence of sickle cell disorders and the mild deletional alpha-thalassaemia among Nigerians is well known, but beta-thalassaemia is believed to be almost nonexistent. Beta thalassaemia trait (BTT) was screened for in patients with unexplained recurrent haemolytic anaemia and healthy individuals.

beta-thalassaemia trait (BTT) was screened for using MCH and HbA2 of 27 pg and 3.5% respectively as cut off in 151 Nigerians which included 29 patients and 122 apparently healthy individuals. The subjects were categorized into four, Group I (high HbA2, low MCH), Group II (low HbA2 and MCH), Group III (high HbA2 and high/normal MCH) and Group IV (normal HbA2 and MCH).

Group I are possible carriers of BTT while group IV are least likely to carry either alpha or beta thalassaemia genes. There were 36 (26%), 39 (28%), 27 (19%) and 38 (27%) in groups I-IV respectively. The mean MCH, MCV, haematocrit and HbA2 for the study population were 26 +/-2.8, 81 +/- 7.9, 37.5 +/- 6.8 and 3.4 +/- 1.7 respectively. The mean MCV and haematocrit were significantly lower for group I compared to group IV (76.9 Vs 86.6, p = 0.00) and (36.5Vs39.7, p = 0.03) respectively. Group II had significantly lower MCV and haematocrit than group IV (75.4 (p = 0.00) and 36.4 (p = 0.01) respectively. There was a positive correlation between the MCH and MCV with the haematocrit (p = 0.004, p = 0.001 respectively) but HbA2 showed a stronger negative correlation with the haematocrit (p < 0.0001).

This does not only show the presence of BTT, but a higher prevalence than previously thought, mutations responsible for it should therefore be characterized.