Objective: Evaluation of the Dutch national screening programme for phenylketonuria (PKU).
Design: Descriptive.
Setting: Nationwide.
Methods: Data on the screening were obtained from the laboratories, from the registration offices of vaccination and screening results and from the paediatricians to whom infants with positive screening values were referred, during the period from September 1st, 1974 to December 31st, 1993.
Results: During the study period 3,481,738 infants were screened in the Netherlands (99.4% of all live births). The sensitivity of the programme was 98%, the specificity 99.99% and the positive predictive value 50%. The prevalence of PKU varied considerably between regions, e.g. from 1:33,600 in Zuid-Holland to 1:8,250 in Limburg (average in the Netherlands 1:18,000). The percentage of patients treated before the age of 22 days was 84% in the period from 1974 to 1988 and 95% in the period from 1989 to 1993 (p = 0.04). Birth weight in patients with PKU was 141 g (95% confidence interval: 66-216) less than the expected birth weight in the Netherlands. Furthermore, a slight growth retardation occurred in the first three years of life in early treated patients. The percentage of patients following special education was twice as high as in the general population (p < 0.001).
Conclusion: The screening procedure for PKU is functioning at a high level. Despite early treatment development of patients with PKU is slightly below normal.