Utilisation of predictive, prenatal and diagnostic testing for Huntington's disease in Johannesburg

Huntington's disease (HD) is a dominantly inherited condition in which the gene defect is known. As such individuals in at-risk families can be tested before symptoms occur, prenatally, or after symptoms appear to confirm the diagnosis.

To investigate the utilisation and sequelae of the predictive, prenatal and diagnostic services offered to families with suspected Huntington's disease.

A retrospective design was used. The 1975-1997 records of the Department of Human Genetics for all families with a history of HD presenting for genetic counselling and DNA analysis were studied.

Department of Human Genetics, South African Institute for Medical Research and University of the Witwatersrand, Johannesburg.

There were 30 at-risk (50% risk) subjects for predictive testing, 7 women (10 pregnancies) for prenatal testing, and 52 subjects for diagnostic testing.

These were provided by the results from molecular studies and by the action taken by subjects after a predictive or prenatal result was given.

Altogether 15 (50%) subjects for predictive testing had a positive result, but none had serious psychiatric sequelae. Two women were found to be carrying an affected fetus and both requested pregnancy termination. Of 52 diagnostic tests, 33 (63%) were positive.

The service was used appropriately, and there were no traumatic incidents following positive results. There was no genotypic or sex bias in subjects presenting for testing. Black and white patients were equally likely to be positive for HD on diagnostic testing. The families appreciated the service and found it useful in the detection and prevention of HD.