DBS should be collected and the specimen is to be sent to the neonatal screening laboratory. A second NBS card is to be collected on any positive screens.

APPLICATION:  Investigation of a neonate with a reducing substance in urine that is not glucose.  Definitive diagnosis of galactosaemia in a baby with a positive neonatal screening test is through genetic results along with the patients LFT and coag profiles.  

INTERPRETATION:  Patients with classical galactosaemia have no detectable activity.  The Duarte mutation has 50% of residual activity so that the Duarte-galactosaemia compound heterozygotes have about 25% normal activity.  As the enzyme is somewhat heat-labile, dried blood spots on neonatal screening cards posted to a central laboratory may show falsely low values.