Results of routine screening for phenylketonuria in early infancy, Northern Ireland (1960-67).

The routine screening of newborns for phenylketonuria (PKU) was started in Northern Ireland during the early part of 1960. The method used initially was the Phenistix/napkin test, i.e. a Phenistix strip (Ames Labs.), was pressed between the folds of a wet napkin. Tests were carried out by Health Visitors on infants aged between 3 and 6 weeks. Because this screening procedure was not adopted by Public Health Authorities of all six Counties at the same time, many newborns in the Province were not screened during the early part of this survey. This accounts for the fact that the number of children screened between January 1960 and December 1963 constitutes only slightly over 50% of the total births during this period (Table). The results of Phenistix testing proved disappointing, and clearly demonstrated the unreliability of the test as a screening procedure. Whereas 2 patients with phenylketonuria were discovered using this screening technique during 1960-63, 4 others, recorded as having a negative Phenistix/ napkin reaction, were later shown to be suffering from the disorder. Yet, laboratory trials using fresh samples of liquid urine from a large number of known phenylketonuric patients all gave a positive reaction on testing with Phenistix strips. It seemed, therefore, that the recorded false negative Phenistix/napkin screening results were more likely to have been due to errors in technique in performing