Nine conditions in the UK programme, taken at day 5
Expansion
Taken by heel prick at day 5, the UK programme currently screens for:
- Phenylketonuria
- Congenital hypothyroidism
- Sickle cell disease
- Cystic fibrosis (immunoreactive trypsinogen, then genetic testing)
- MCADD (medium chain acyl-CoA dehydrogenase deficiency)
- Maple syrup urine disease
- Isovaleric acidaemia
- Glutaric aciduria type 1
- Homocystinuria
The common thread is that each is serious, treatable, and causes irreversible harm if detected only once symptomatic. Phenylketonuria and congenital hypothyroidism both cause preventable intellectual disability; MCADD causes sudden hypoglycaemic death that simple fasting avoidance prevents.
Timing matters: sampling before feeding is established gives false negatives for phenylketonuria, since phenylalanine must have been ingested; and sampling too early gives false positives for congenital hypothyroidism because of the normal neonatal TSH surge.
Screening is not diagnostic: a positive result requires confirmatory testing, and parents should be told this when recalled.