There have been significant advances in the methods available for the detection and investigation of individuals with inherited metabolic disorders. The burgeoning of molecular biology in recent years and the discovery of new classes of inherited metabolic disorders, such as inborn errors of fat oxidation, are well known. What is perhaps less well recognised, is that there have been comparable advances in analysis and laboratory automation. The combination of the development of generic analytical technology of great power and sophistication, and the discovery of new treatable metabolic diseases detectable in the newborn period, has, we believe, resulted in a sea change in neonatal screening.

Neonatal screening for metabolic diseases became feasible as a result of the pioneering work of Guthrie. He developed a simple, robust, and effective technique for the detection of elevated concentrations of phenylalanine in blood—the “Guthrie Test”— which was used to detect phenylketonuria by means of a semi-quantitative microbiological bioassay.1 Screening for this disorder (PKU; phenylalanine hydroxylase deficiency; McKusick 261600) was subsequently implemented in the UK in 1969.2The specimens used are dried blood spots which are usually collected by means of a heel-prick on the sixth day of life, although later sampling, up to 14 days, can occur. This form of specimen collection has become almost universal. Quantitative assays specific for phenylalanine have been introduced by some centres, driven by the desire to introduce a degree of automation.3 4 An alternative approach is to use chromatographic methods, and this has been adopted by some centres.5 The proponents of this technology contend that other inherited disorders of amino acid metabolism can be detected and that improved prognosis may be achieved by early diagnosis. However, chromatographic methods are time consuming and difficult to automate, particularly in respect of the recognition of abnormal chromatograms. None …