Fig. 6.

Classical Phenylketonuria (PKU) example. In the classical PKU example, exposure to phenylalanine in the diet only gives clinical symptoms (PKU-SYNDROME) in people with a mutation in the gene coding for the hepatic enzyme phenylalanine hydroxylase (PAH-MUTATION). We assume a population (N = 1,000,000) with 90% of the people exposed and 10% non-exposed to phenylalanine in the diet. In this population, 50 individuals present the PAH-MUTATION. Among the people with the mutation, 90% are exposed and 10% are non-exposed to phenylalanine in the diet. The figure shows the values of the true positive fraction (TPF), false positive fraction (FPF), relative risk (RR) and population attributable fraction (PAF) in both the general population (left) and in the strata of people with the PAH-MUTATION (right).