The failure to diagnose inborn errors of metabolism in New Zealand: the case for expanded newborn screening.
OBJECTIVE
Expanded newborn screening uses a new technology, tandem mass spectrometry, to diagnose an additional 20 plus rare treatable inborn errors of metabolism based on the further analysis of the current newborn Guthrie card blood sample. The purpose of this study was to investigate the incidence of these disorders in New Zealand, based on clinical diagnosis rates, and compare these to the incidence, based on the established expanded newborn screening programme, in New South Wales, Australia.


METHODS
Over a 3-year period, the cases of inborn errors of metabolism notified to the New Zealand Paediatric Surveillance Unit and/or identified by the relevant metabolic laboratories were recorded and compared to the incidence rates during the same period in New South Wales.


RESULTS
There were 175,000 and 270,000 births in New Zealand and New South Wales respectively during the study period. Eight cases of treatable inborn errors (potentially diagnosable by newborn screening) were diagnosed in New Zealand compared to 41 (including two prior to screening) in New South Wales. The disorder medium chain acyl Co-A dehydrogenase deficiency was diagnosed twice in New Zealand and in 24 newborn infants in New South Wales.


CONCLUSIONS
Without expanded newborn screening, inborn errors of metabolism are under-diagnosed in New Zealand. This study supports the recent establishment of screening in New Zealand.
Wilson
Callum
C
Newborn Metabolic Screening Unit, LapPlus, Auckland City Hospital, Auckland. callumw@adhb.govt.nz
Kerruish
Nicola J
NJ
Wilcken
Bridget
B
Wiltshire
Esko
E
Webster
Dianne
D
D006801:Humans; D015994:Incidence; D007231:Infant, Newborn; D008661:Metabolism, Inborn Errors / Q000097:blood / Q000175:diagnosis* / Q000453:epidemiology; D015997:Neonatal Screening / Q000379:methods / Q000706:statistics & numerical data*; D009517:New South Wales / Q000453:epidemiology; D009520:New Zealand / Q000453:epidemiology; D017064:Process Assessment, Health Care; D053719:Tandem Mass Spectrometry