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...
