New technologies enable faster and broader screening for inborn metabolic disorders. Information can be obtained nowadays about many metabolites through one test using tandem mass spectrometry (TMS). As well, new therapies for lysosomal storage diseases open the prospects for new screening programs for these disorders. Indeed, the development of screening tests for these disorders is in advanced stages.
The decision on what metabolites to include in a screening program that uses one‐test‐many‐results technology and what diseases to screen for when developing specific screening tests rests with screening policy makers. There are disorders for which there is solid evidence that newborn screening is unequivocally beneficial (e.g., congenital hypothyroidism). However, should we wait for evidence for every disorder? Not waiting might impose an enormous cost without proven benefit (e.g., Pompe disease). Waiting may cost in infants' lives and disability (e.g., glutaric aciduria type I, congenital adrenal hyperplasia). Clinicians should, and do, play a pivotal role in this process, being responsible for communicating results to families and treating the diagnosed infants.
The results obtained from TMS screening represent the biochemical phenotype of the infant, the result of his/her genetic makeup, age, diet and possibly other environmental factors. Some infants who manifest the biochemical alterations suggestive of severe metabolic diseases are clinically asymptomatic. Scientists aim to improve accuracy and specificity of detected metabolites. Clinicians aim to improve the specificity of the diagnosis by organising additional tests and tailoring individual therapeutic regimens. The challenge for both disciplines is to combine their experience into a comprehensive view that will enable sensitive, specific and evidence based screening programs.