Application of polymerase chain reaction to the prenatal diagnosis of sickle cell anaemia in Nigeria.

Although sickle-cell disease is very common in Nigeria, control by prenatal testing is lacking. The polymerase chain reaction-based technology combined with chorionic villi sampling has enabled us to offer prenatal diagnosis of sickle cell disease to 50 pregnant women who were at risk of bearing children with sickle cell anaemia. DNA was extracted from the villus and subjected to either PCR and restriction enzyme (Dde I) analysis (36 samples) or to PCR-ARMS procedure (12 samples) or to both procedures when the results by the first procedure were equivocal (2 samples). The genotypic distribution was 13AA, 25AS and 11SS. In one case, it was not possible to determine the genotype of the villi by both methods. A post delivery genotype analysis confirms the correctness of prenatal diagnosis in all the 42 subjects that has so far reported. The results clearly demonstrate the usefulness of the PCR method in the prenatal diagnosis of sickle-cell anaemia in this environment.

Initiation of prenatal diagnosis of sickle-cell disorders in Africa.

We introduced prenatal diagnosis of SCD in Nigeria in order to meet a rising demand. Our approach and experience are documented as a guide to others in countries with similar problems. A cost-recovery fee charged only to sustain the service predictably limited access to it. Ultrasound-guided transcervical (TC) or transabdominal (TA) sampling of 124 chorionic villi was done from nine weeks' gestation. All couples carried the sickle trait (AS) and 52 (51 per cent) women had previously had children with sickle-cell anaemia. 72 samples were obtained by the TA and 52 by the TC route. 7.2 per cent miscarried after CVS but the miscarriage rate was significantly higher (p=0.023) after TC CVS (13.5 per cent) than after TA CVS (2.8 per cent) and also higher in the first 62 (11.3 per cent) than after the last 62 CVS (3.2 per cent). DNA analysis of CVS indicated Hb AA in 29 (23.4 per cent), AS in 67 (54 per cent) and SS in 23 (18.5 per cent). No result was obtainable in five subjects for technical reasons. 96 per cent of the women with SS fetuses terminated the pregnancies. The need for a standby source of electricity where supply is unreliable and for providing an equitable service to all couples at risk are highlighted.