Plasma specimen must be transported immediately to the laboratory on a cold pack. (Specimens must reach the laboratory and be centrifuged within 2 hours of collection).

If ELFT is requested along with this test, an extra PST is not required so long as full tube requirements have been collected for metabolic screen.

Serum can also be used.

APPLICATION:  Diagnosis and monitoring of phenylketonuria and maternal hyperphenylalaninaemia.

INTERPRETATION:  An increased level at neonatal screening indicates phenylketonuria or hyperphenylalaninaemia.  If the level exceeds
1,200 µmol/L,  phenylketonuria is present.  Satisfactory level on diet can be up to 250 µmol/L with good control, but should not be less than 40 µmol/L.  During pregnancy, levels should be as close as possible to 120 µmol/L.