The use of tandem-mass spectrometry for neonatal screening has increased greatly in the last 10 years. In Australia all infants are screened in this way and the disorders most frequently diagnosed are medium-chain acyl-CoA dehydrogenase (MCAD) deficiency and phenylketonuria. There are few reports of outcomes after screening for rare disorders, but a nationwide Australian study of the effectiveness of screening by tandem-mass spectrometry for MCAD deficiency has now been …