When the inheritance of two heterozygote states become a diagnostic problem: misdiagnosis of the sickle cell trait.

BACKGROUND

The sickle cell trait is a benign asymptomatic condition that should not ordinarily be associated with clinical manifestations of a haemoglobinopathy.

METHOD: This is a case control study of sickle cell trait patients who presented with symptomatology of a haemoglobinopathy. HbA2, HbF and HbS levels as well as the haematocrit and the peripheral film pictures of 10 symptomatic individuals (patients) with the sickle cell trait were compared with those of 20 asymptomatic individuals (controls) with the sickle cell trait.

RESULTS

The mean HbA, of the cases was 4.9% compared to the mean of 2.2% for the controls (p < 0.0001). Nine of the patients and none of the controls had a raised HbA, (> 3.5%). The mean HbF of the patients was 5.6% with a range of 1.2-14.0% while the mean of the control was 2.0% and a range of 0. 7-8.4% (p = 0.006). Six (30%) of the controls had normal HbF level (<1%) while none of the patients had a normal HbF level. The mean haematocrit of the patients and controls were 0.33 and 0.37 respectively (p = 0.009). HbS level was below 40% in both groups. Pregnancy did not significantly affect the mean HbF, the mean HbF for pregnant and non-pregnant cases were 2.1% and 3.8% respectively.

CONCLUSION

These findings suggest that the prevalence of the thalassaemia trait may be higher among Nigerians than previously thought with the clinical severity masked by the co-inheritance of other genes like thalassaemia that occur frequently in the same population.