title: Newborn bloodspot results: predictive value of screen positive test for thalassaemia major.
abstract: OBJECTIVE
  There are limited published data on the performance of the percentage of haemoglobin A (Hb A) as a screening test for beta thalassaemia major in the newborn period. This paper aims to analyse data derived from a national newborn bloodspot screening programme for sickle cell disease on the performance of haemoglobin A (Hb A) as a screening test for beta thalassaemia major in the newborn period.
  
  
  METHODS
  Newborn bloodspot sickle cell screening data from 2,288,008 babies were analysed. Data reported to the NHS Sickle Cell and Thalassaemia Screening Programme in England for the period 2005 to 2012 were also reviewed to identify any missed cases (4,599,849 babies).
  
  
  RESULTS
  Within the cohort of 2,288,008 births, 170 babies were identified as screen positive for beta thalassaemia major using a cut-point of 1.5% HbA. There were 51 identified through look-back methods and 119 prospectively identified from 4 screening laboratories. Among 119 babies with prospective data, 7 were lost to follow up and 15 were false positive results. Using a cut-off value of 1.5% Hb A as a percentage of the total haemoglobin as a screening test for beta thalassaemia major in the newborn provides an estimated sensitivity of 99% (from the look back arm of the study) with a positive predictive value of 87% (from the prospective arm of the study). Excluding infants born before 32 weeks gestation, the positive predictive value rose to 95%.
  
  
  CONCLUSIONS
  A haemoglobin A value of less than 1.5% is a reliable screening test for beta thalassaemia major in the newborn period.
authors.affiliation: NHS Sickle Cell and Thalassaemia Screening Programme, King's College School of Medicine, 6th Floor, Capital House, 42 Weston Street, SE1 3QD, London.
authors.forename: Allison
authors.initials: A
authors.lastname: Streetly
authors.forename: Radoslav
authors.initials: R
authors.lastname: Latinovic
authors.forename: Joan
authors.initials: J
authors.lastname: Henthorn
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Daniel
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Dormandy
authors.forename: Phil
authors.initials: P
authors.lastname: Darbyshire
authors.forename: Debbie
authors.initials: D
authors.lastname: Mantio
authors.forename: Laura
authors.initials: L
authors.lastname: Fraser
authors.forename: Lisa
authors.initials: L
authors.lastname: Farrar
authors.forename: Andrew
authors.initials: A
authors.lastname: Will
authors.forename: Lesley
authors.initials: L
authors.lastname: Tetlow
mesh_terms: D000755:Anemia, Sickle Cell / Q000175:diagnosis; D005260:Female; D006441:Hemoglobin A / Q000032:analysis; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D015997:Neonatal Screening / Q000379:methods*; D017086:beta-Thalassemia / Q000175:diagnosis*
chemical_list: D006441:Hemoglobin A
keywords: Screening; beta thalassaemia; haemoglobin A; newborn; screening programme; sickle cell disease; test predictive value