title: Evaluation of the revised New Zealand national newborn screening protocol for congenital hypothyroidism.
abstract: OBJECTIVE
  The aim of this study was to assess the performance of the revised New Zealand (NZ) newborn screening TSH cut-offs for congenital hypothyroidism (CHT).
  
  
  METHODS
  Screening data over 24 months were obtained from the NZ newborn metabolic screening programme, which utilizes a 2-tier system of direct clinical referral for infants with markedly elevated TSH, and second samples from those with mild TSH elevation. We evaluated the impact of a reduced TSH threshold (50 to 30 mIU/l blood) for direct notification and a lower cut-off (15 to 8 mIU/l blood) applied to second samples and babies older than 14 days.
  
  
  RESULTS
  In 2013 and 2014, 117 528 infants underwent newborn screening for CHT. Fifty-two CHT cases were identified by screening (47 general newborn population, five repeat testing in low-birth-weight infants) and one case was missed. Thirty-two infants with screening TSH ≥30 mIU/l were directly referred at a median of 9 days (5-14) and 15 with TSH 15-29 mIU/l were referred after a second sample at a median of 20 days (9-52, P < 0·001). All directly referred infants were confirmed as CHT cases with no earlier referrals as a result of the reduced threshold. The lower TSH cut-off applied to second samples lead to the identification of six extra cases of CHT (15% increase) from seven extra clinical referrals.
  
  
  CONCLUSIONS
  The NZ screening programme achieved a 15% increase in CHT case detection for minimal increase in workload or anxiety for families of healthy infants. A further decrease in the threshold for direct referral may allow earlier diagnoses.
authors.affiliation: New Zealand Newborn Metabolic Screening Programme, LabPlus, Auckland District Health Board, Auckland, New Zealand.|Starship Children's Hospital, Auckland District Health Board, Auckland, New Zealand.
authors.forename: Natasha L
authors.initials: NL
authors.lastname: Heather
authors.affiliation: Starship Children's Hospital, Auckland District Health Board, Auckland, New Zealand.|Liggins Institute, University of Auckland, Auckland, New Zealand.
authors.forename: Paul L
authors.initials: PL
authors.lastname: Hofman
authors.affiliation: New Zealand Newborn Metabolic Screening Programme, LabPlus, Auckland District Health Board, Auckland, New Zealand.
authors.forename: Mark
authors.initials: M
authors.lastname: de Hora
authors.affiliation: New Zealand Newborn Metabolic Screening Programme, LabPlus, Auckland District Health Board, Auckland, New Zealand.
authors.forename: Joan
authors.initials: J
authors.lastname: Carll
authors.affiliation: Liggins Institute, University of Auckland, Auckland, New Zealand.
authors.forename: José G B
authors.identifier: http://orcid.org/0000-0003-1226-1956
authors.initials: JG
authors.lastname: Derraik
authors.affiliation: New Zealand Newborn Metabolic Screening Programme, LabPlus, Auckland District Health Board, Auckland, New Zealand.
authors.forename: Dianne
authors.initials: D
authors.lastname: Webster
mesh_terms: D002985:Clinical Protocols; D003409:Congenital Hypothyroidism / Q000175:diagnosis* / Q000453:epidemiology; D006801:Humans; D007231:Infant, Newborn; D015997:Neonatal Screening / Q000379:methods* / Q000592:standards; D009520:New Zealand; D012016:Reference Values; D013972:Thyrotropin / Q000097:blood* / Q000592:standards
chemical_list: D013972:Thyrotropin