A simplified test to detect PKU heterozygotes by discriminant analysis in mentally retarded children and their mothers.

We have developed classification coefficients and an equation to detect heterozygotes for phenylketonuria. The combination of several variables (Phe, Phe/Tyr, Phe2/Tyr) gave a safe diagnosis in more than 96% of cases. We then computerized a random selection of our population, which was divided into two groups: the first was "selected" to compute discriminant functions, while the second, excluded from computation, was used to check the fitness of our method. Despite the reduction of sample size, 95.2% of unknown subjects were correctly classified. Finally, we used our equation to detect heterozygotes for phenylketonuria in a population of 26 children, affected by non-specific mental retardation, and their mothers. We found a high proportion of carriers for phenylketonuria, defined as subjects having a percent probability of correct classification higher than 90. By this method, heterozygosity was detected in two child-mother couples, four individual children and five mothers.