title: Age independent first trimester screening for Down syndrome: improvement in test performance.
abstract: OBJECTIVE
  The aim of this study was to compare screening performance for Down syndrome of the absolute risk (AR) method to the first trimester combined test (FCT) at different maternal ages.
  
  
  METHODS
  There was a retrospective analysis of 32,448 FCT. AR was defined as final risk divided by maternal age risk.
  
  
  RESULTS
  The likelihood of receiving a true prediction was comparable between both methods in all age groups. With the AR method, two extra Down syndrome cases were detected in women <30 years, three cases were missed in women ≥36 years, and the likelihood of receiving a false prediction decreased overall (OR 0.82, CI 0.77-0.87; P < 0.0001), in women aged 36-40 years (0.45, CI 0.41-0.51; P < 0.0001), in women aged 41-45 years (0.18, CI 0.13-0.26; P < 0.0001) and increased in women aged ≤25 years (2.12, CI 1.52-2.96; P < 0.004).
  
  
  CONCLUSIONS
  The AR method results in a significant decreased likelihood of receiving a false prediction with a comparable likelihood of receiving a true prediction. Thus, fewer invasive diagnostic tests will be performed. It will take away the misunderstanding about differences in screening performance for women of different ages. This might lead to a higher uptake of first trimester screening resulting in a more efficient screening policy.
authors.affiliation: Department of Obstetrics and Gynaecology, VU University Medical Center, Amsterdam, the Netherlands. m.engels@vumc.nl
authors.forename: M A J
authors.initials: MA
authors.lastname: Engels
authors.forename: J W R
authors.initials: JW
authors.lastname: Twisk
authors.forename: M A
authors.initials: MA
authors.lastname: Blankenstein
authors.forename: J M G
authors.initials: JM
authors.lastname: van Vugt
mesh_terms: D000328:Adult; D004314:Down Syndrome / Q000175:diagnosis*; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D008403:Mass Screening / Q000379:methods; D008423:Maternal Age; D008875:Middle Aged; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D011296:Prenatal Diagnosis / Q000379:methods* / Q000592:standards; D012189:Retrospective Studies