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Newborn phenylketonuria (PKU) Guthrie (BIA) screening and early hospital discharge

W B Hanley1, H Demshar, M A Preston

  • 1Department of Paediatrics, Hospital for Sick Children, Toronto, Ontario, Canada.

Early Human Development
|January 3, 1997
PubMed

Insights

Early hospital discharge may not impact phenylketonuria (PKU) screening sensitivity for classical PKU. However, it could increase missed cases of mild hyperphenylalaninemia (MHP), suggesting screening after 12 hours of age.

Area of Science:

  • Biochemistry
  • Medical Genetics
  • Neonatal Screening

Background:

  • Early postpartum discharge policies raise concerns about reduced sensitivity in Guthrie bacterial inhibition assay (BIA) for phenylketonuria (PKU) screening.
  • This could potentially lead to missed diagnoses of PKU and its variants in newborns.

Purpose of the Study:

  • To assess the impact of early hospital discharge on neonatal screening for PKU and its variants using the BIA method.
  • To evaluate the sensitivity and specificity of the BIA test in relation to infant age at blood sample collection.

Main Methods:

  • Conducted 18 standard BIA screening tests on 11 newborn infants diagnosed with PKU.
  • Collected blood spot samples at various intervals from 1 to 24 hours after birth.
  • Analyzed samples using the routine screening protocol at the Ontario Ministry of Health newborn screening laboratory.

Main Results:

  • Most blood samples showed phenylalanine levels ≥ 240 mumol/l, regardless of infant age, except for one sample from an infant with mild hyperphenylalaninemia (MHP) at 4 hours.
  • Over 29 years, with a cutoff of 240 mumol/l for samples ≥ 24 hours old, sensitivity was 99.2% for classical and mild PKU, with few false negatives.
  • Specificity was 99.9% for infants screened after 24 hours, but early discharge may increase missed MHP cases.

Conclusions:

  • Early discharge may not significantly affect the detection of classical and mild PKU via BIA.
  • However, early discharge is likely to increase the number of missed MHP cases when using the BIA with a 240 mumol/l cutoff.
  • Recommend that neonates be at least 12 hours old for initial BIA PKU screening, with further prospective studies needed.

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