Experience based on 800,000 newborn screening tests of the Budapest Phenylketonuria Centre.

800 000 newborns were screened for hyperphenylalaninaemia by the Guthrie-test in the Budapest PKU Centre in the 10 and a half years since 1 May, 1973. The blood samples were taken from mature newborns on the fifth and from premature babies on the fourteenth day of life. All infants exhibiting a level equal to or exceeding 12 mg/dl were telegraphically invited to the Centre and those having a level of 15 mg/dl or higher were put on an appropriate diet. The patients were classified according to the result of the phenylalanine tolerance 73 were found to have classical phenylketonuria and 15 had atypical phenylketonuria. The total incidence of phenylketonuria was thus 1: 9091. The mean age at introduction of diet was 30 +/- 15 days during the first period, while 21 +/- 11 days during the second period. Infants having an initial value of 4-12 mg/dl were kept under continuous control; among them 69 were found to have benign hyperphenylalaninaemia (HPA). The PKU/HPA ratio amounted to 1.28. Both screening and care were carried out by the Centre, and the practice of care is described in detail. A preliminary evaluation of the therapeutical results with a view of the patients' social class is offered. Phenylalanine levels during the diet were greatly influenced by the familial background and the sociocultural environment.