Tay-Sachs heterozygote screening: specificity and sensitivity.

Heterozygotes for the Tay-Sachs allele can be identified by plotting the heat-labile hexosaminidase activity in serum against the heat-stable activity. Quadratic discriminants can be constructed from homozygous normal and obligate heterozygous data and the probability of misclassification computed. The cost of counseling and the classification error is diminished by the use of 2 tests.