Follow-up study of 16 years neonatal screening for inborn errors of metabolism in West Germany.

Capillary blood samples from almost one million neonates from Baden-Württemberg were investigated for inborn errors of metabolism between 1969 and 1984 in our screening centre. Besides 7 patients with maple syrup urine disease (MSUD), 3 with homocystinuria and 18 with galactosaemia, a follow-up of the positive screening results confirmed 94 patients with phenylketonuria (PKU) and 76 with non-PKU hyperphenylalaninaemia (non-PKU HPA). The incidence of PKU is 1:10000, and that of HPA in the wider sense (PKU and non-PKU HPA) as obtained by newborn screening before further classification at 6 months 1:5532. For West Germany as a whole, the number of newly discovered cases with persistent hyperphenylalaninaemia was 1480 in the same period. The subdivision into PKU and non-PKU HPA is not yet possible from this figure. It is strongly suggested that the abnormal results of newborn screening for phenylalanine be designated as hyperphenylalaninaemia (in the wider sense) and that the terms "PKU" or "non-PKU HPA" be used only after further differentiation as carried out by us at the age of 6 months.