A 3-year cytogenetic survey of 9 661 patients in South Africa.

During the period 1 January 1977 - 31 December 1979, 9 661 patients underwent cytogenetic investigation at seven participating laboratories in South Africa. The chromosome data were coded using a standard protocol and the results tabulated, being listed according to the clinical signs which led to referral for investigation. Cytogenetic investigation was most commonly requested for prenatal studies, and 22% of the group's effort was directed towards this. One in 27 amniotic cell specimens was reported to have shown anomalous chromosomes, trisomy 21 being the most frequent abnormality. The majority of postnatal investigations were requested because congenital abnormalities suggested an underlying chromosomal defect. In 42,3% of 2 420 patients a chromosome defect was confirmed. Results of chromosome studies are tabulated by indication for referral and the findings summarized. This collaborative study gives an indication of the nature and frequency of chromosome disorders in South Africa.