Human Reproduction, Vol. 17, No. 5, 1358-1362,
May 2002
© 2002 European Society of Human Reproduction and Embryology
Comparison between disclosure and non-disclosure approaches for trisomy 21 screening tests
Department of Obstetrics and Gynecology, Assaf Harofeh Medical Center, Zerifin and Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
BACKGROUND: First-trimester nuchal translucency (NT) and second-trimester triple test (TT) are common screening programmes for trisomy 21. The aim of this study was to compare disclosure and non-disclosure approaches of combining those tests. METHODS: Likelihood ratios of both NT and TT tests, among 508 normal and 23 trisomy 21-affected pregnancies, were used for calculating population-adjusted risks. Disclosure approach incorporated all cases which, by either NT or TT, exhibited a risk 
1:250 whereas non-disclosure approach generated a new integrated figure 1:250. RESULTS: Among women aged 
34 years, the disclosure and non-disclosure approaches were associated with false positive rates of 4.3 and 1.1%, detection rates of 76.4 and 61.2%, positive predictive value (PPV) of 1:53 and 1:17, and false negative rate of 1:3129 and 1:1985 respectively. CONCLUSIONS: The disclosure approach resulted in considerably higher detection rates. The non-disclosure approach, however, was four times better regarding the number of invasive procedures required to detect one case of trisomy 21. However, the positive predictive value associated with the disclosure policy was still much more beneficial than that obtained in women aged 
37 years, who are routinely referred to fetal karyotyping.
Key words: disclosure/non-disclosure/nuchal translucency/triple test/trisomy 21
1 To whom correspondence should be addressed at: Department of Obstetrics and Gynecology, Assaf Harofeh Medical Center, Zerifin, 70300 Israel. E mail: aherman{at}asaf.health.gov.il