An increase in cost-effectiveness of first trimester maternal screening programmes for fetal chromosome anomalies is obtained by contingent testing.
We assessed the discriminatory efficiency and cost-effectiveness of a novel way of organising first trimester screening for Down syndrome (DS), contingent testing, where a serological test (PAPP-A and beta-hCG: the double test) is made in early first trimester and followed by nuchal translucency testing (NT) only in women with an intermediate risk, e.g. <1:65 and >1:1000, and not in all women as in normal first trimester screening (NFTS). Using Monte Carlo simulation contingent testing had a detection rate (DR) of 78.9% and a false-positive rate (FPR) of 4.0% for DS with 19.4% of women offered NT testing. The DR of NFTS was 85.5% and the FPR 4.4%. The decrease in NT screening was associated with an increase from 23% to 29% in the proportion of DS cases born. The cost of the contingent testing programme was pound 53,000 per DS case not born and pound 91,000 in NFTS. The number of aborted fetuses per DS case were 0.35 and 0.36, respectively. Thus, contingent testing is an organisation of first trimester screening where costs can be reduced with a marginal decrease in performance. Contingent testing is attractive in areas where NT screening is the bottleneck preventing the introduction of first trimester screening.
Department of Clinical Biochemistry, Statens Serum Institut, Copenhagen, Denmark. mic@ssi.dk
Michael
M
Christiansen
Severin
S
Olesen Larsen
D018997:Chorionic Gonadotropin, beta Subunit, Human / Q000097:blood; D002869:Chromosome Aberrations; D003362:Cost-Benefit Analysis; D004314:Down Syndrome / Q000175:diagnosis*; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D008403:Mass Screening / Q000191:economics*; D008423:Maternal Age; D009333:Neck / Q000000981:diagnostic imaging / Q000196:embryology; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D011266:Pregnancy-Associated Plasma Protein-A / Q000032:analysis; D011296:Prenatal Diagnosis / Q000191:economics*; D012307:Risk Factors; D016216:Ultrasonography, Prenatal
D018997:Chorionic Gonadotropin, beta Subunit, Human; D011266:Pregnancy-Associated Plasma Protein-A