[21 years "Austrian Program for Early Detection of Congenital Metabolic Abnormalities." Did the screening programs...

Before the introduction of the programme for the early detection of inborn errors of metabolism the discovery of the biochemical abnormality was merely the proof of a diagnoses based on characteristic features. Neonatal screening inverted the process and the biochemical anomaly became primary marker and symptoms were prevented by treatment. In reality, the subsequent development of symptoms was uncertain. In this way a great number of hitherto unknown metabolic anomalies was discovered. Screening methods for the first time allowed correct determination of the incidence of inherited disorders in different population. Important differences were uncovered intra- and internationally. Screening centres performing psychometry not only in homozygote patients, but also in heterozygote parents found that the heterozygotes for phenylketonuria (PKU) in spite of normal blood phenylalanine levels, are slightly subnormal intellectually. This is true also for early- and satisfactory-treated homozygotes. Increased intracellular phenylalanine concentrations in both could explain this slight intellectual subnormality which is, apparently, independent of the blood level. At least three treatment centres observed a decrease in IQ of 9 to 13 points between 1 and 8 years of age in early- and well-treated PKU patients being mostly still in the normal range. The IQ curves are parallel for these tree centres and independent of the age of diet discontinuation.