Organic acid concentrations were quantified by gas chromatography and the individual acids identified by mass spectrometry in urine specimens from a healthy Turkish pediatric population of ages 2 days to 16 years, subdivided into five age groups. We quantified 69 organic acids (32 major and 37 minor components) and report here the median values and percentiles for each compound, adjusted for creatinine content, for the five groups. Concentrations of most of the organic acids tend to decrease with age but display substantial differences between age groups. This emphasizes the importance of comparing patients' data with age-matched reference data. Correlations between the excretion of organic acids and protein or caloric intake were significant for several compounds.

Blood obtained by finger prick from 209 presumed normal homozygotes and 42 heterozygotes for classical PKU was analyzed for plasma phenylalanine (Phe) and tyrosine (Tyr) by a fluorimetric method. Subjects were tested near midday and 3 hours after a protein-rich breakfast. The plot of Phe/Tyr (micromolar ratio) against Phe2/Tyr, permitted the detection of 11 heterozygotes among 209 controls. The accuracy of this method was checked by computation of a stepwise multivariate discriminant analysis, using Phe and Tyr (mumol/L), Phe/Tyr micromolar ratio and Phe2/Tyr as variables. Ten of the 11 subjects were recovered with a percentage of correct classification of over 90%, while one case had a percentage of 89.45%. The PKU gene frequency was found to be 1/19. This emphasizes the importance of a screening programme for PKU gene carrier status in Turkey.