Newborn screening for congenital hypothyroidism: improved assay performance has created an evidence gap

Newborn screening for congenital hypothyroidism in very‐low‐birth‐weight babies: the need for a second test

“…This number suggests that transient hyperthyrotropinaemia may be more common in infants with VLBW, and it is not known how this might affect developmental outcome. Pollitt suggests that 'additional' cases of hypothyroidism are being found because of better analytical performance in screening laboratories, and that identifying and treating either mild or transient hypothyroidism does not accord with currently accepted criteria for screening (Pollitt and Wales 2010). Long-term neurodevelopmental studies in a large number of infants and children are needed to evaluate the effects of subtle thyroid function abnormalities in neonates (Rapaport 2000), and this might need to be a retrospective study similar to the instructive study of Alm and colleagues (Alm et al 1984)a ss u g g e s t e d (Pollitt and Wales 2010).…”

Impact of new screening technologies: should we screen and does phenotype influence this decision?

“…The potential benefits of screening are often considered from the standpoint of the classical clinically presenting form of the condition. The challenge is to recognise that screening will reveal variants that either would not merit screening (Pollitt and Wales 2010) or would require a more subtle and graded response. This is particularly difficult for some metabolic disorders that can often be thought of as "risk factors" rather than overt progressive disease.…”

New technologies extend the scope of newborn blood‐spot screening, but old problems remain unresolved

“…(16) showed otherwise: at the age of five years, only half the cases with increased thyrotropin (TSH) in the newborn screening sample had been diagnosed clinically with hypothyroidism, the others being at most only mildly affected or biochemically normal. Over recent years, there have been further increases in the rate of ‘screening‐positive’ diagnoses, partly because of demographic changes (17), but also as improved assay sensitivity has led to cut‐offs being correspondingly reduced (18,19). Many of these additional cases have ‘sub‐clinical’ or ‘compensated’ hypothyroidism, showing persistently increased TSH concentrations but plasma thyroxine within the normal range.…”