Phenylketonuria: a reassessment of mass infant screening by napkin test.

Most local health authorities in Great Britain have used the Phenistix test on wet napkins or diapers (napkin-Phenistix test) to screen all young infants for phenylketonuria (Centerwall et al., 1963). This test is a sensitive and reliable method of detecting phenylpyruvic aciduria (Gibbs and Woolf, 1959; Woolf, 1963), which is an early sign of true phenylketonuria (Allen et al., 1964; Berry and Wright, 1967). Some practical difficulties have been emphasized by Hudson and Ireland (1959), but information is lacking on the effectiveness of the napkin test in mass detection programmes. In the Birmingham screening survey (Boyd, 1961) one case was found out of 18,981 tested, which was thought to be adequate, assuming a regional incidence of one in 20,000 births. In Edinburgh a similar incidence was predicted, but the one expected case was missed (Farquhar et al., 1962).