title: Screening of neonatal UK dried blood spots using a duplex TREC screening assay.
abstract: OBJECTIVE
  Severe Combined Immunodeficiency (SCID) is considered to be a paediatric emergency and unless identified promptly can be life-threatening. Frequently, infants are not diagnosed with SCID until they have become seriously ill with infection leading to treatment complications and a poorer prognosis. We aimed to test a newly available commercial duplex assay to measure T cell receptor excision circles (TRECs) to establish if this would be suitable for newborn screening for SCID in the UK.
  
  
  METHODS
  Over 5000 anonymous retrospective dried blood spots (DBS) were used alongside 18 confirmed SCID positive DBS with a newly available duplex assay to measure TRECs levels and control gene levels. We also included testing of premature babies and babies from neonatal intensive care units (NICU) as these have been shown to have high false positive rates in other TREC screening assays.
  
  
  RESULTS
  All 18 SCID DBS samples were successfully identified as SCID positives in the study. The number of presumptive positives detected was dependent on the TREC cut-off threshold settings. When analysed with five different TRECs cut-off values (20, 25, 30, 35 and 40 TREC copies/μl blood) the presumptive positive rate ranged from 0.04 to 1.00 % of samples tested. Premature infants and neonates from NICU did not show high presumed false positive rates in this assay.
  
  
  CONCLUSIONS
  The study demonstrated that this duplex assay kit will identify all newborns with SCID as presumptive positives. The data also shows that with suitable TREC cut-off settings the number of presumptive positives from non-SCID newborns will be manageable in the context of a national screening service.
authors.affiliation: Haematology, Cellular and Molecular Diagnostic Service, Great Ormond Street Hospital for Children, London, UK, stuart.adams@ucl.ac.uk.
authors.forename: Stuart P
authors.initials: SP
authors.lastname: Adams
authors.forename: Samina
authors.initials: S
authors.lastname: Rashid
authors.forename: Tharindu
authors.initials: T
authors.lastname: Premachandra
authors.forename: Katie
authors.initials: K
authors.lastname: Harvey
authors.forename: Adeboye
authors.initials: A
authors.lastname: Ifederu
authors.forename: Melanie C
authors.initials: MC
authors.lastname: Wilson
authors.forename: H Bobby
authors.initials: HB
authors.lastname: Gaspar
mesh_terms: D000465:Algorithms; D002675:Child, Preschool; D005820:Genetic Testing / Q000379:methods*; D005865:Gestational Age; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D015997:Neonatal Screening / Q000379:methods*; D011933:Reagent Kits, Diagnostic; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D016511:Severe Combined Immunodeficiency / Q000175:diagnosis*
chemical_list: D011933:Reagent Kits, Diagnostic