Comparison between disclosure and non-disclosure approaches for trisomy 21 screening tests.
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 > or = 1:250 whereas non-disclosure approach generated a new integrated figure > or = 1:250.


RESULTS
Among women aged < or = 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 > or = 37 years, who are routinely referred to fetal karyotyping.
Herman
Arie
A
Department of Obstetrics and Gynecology, Assaf Harofeh Medical Center, Zerifin, Israel. aherman@asaf.hjealth.gov.il
Dreazen
Eli
E
Tovbin
Joseph
J
Weinraub
Zvi
Z
Bukovsky
Yan
Y
Maymon
Ron
R
D000328:Adult; D006063:Chorionic Gonadotropin / Q000097:blood; D030881:Disclosure; D004314:Down Syndrome / Q000175:diagnosis* / Q000000981:diagnostic imaging; D004964:Estriol / Q000097:blood; D005188:False Negative Reactions; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D016013:Likelihood Functions; D009333:Neck / Q000000981:diagnostic imaging; D011237:Predictive Value of Tests; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D011262:Pregnancy Trimester, Second; D011296:Prenatal Diagnosis; D016216:Ultrasonography, Prenatal; D000509:alpha-Fetoproteins / Q000032:analysis
D006063:Chorionic Gonadotropin; D000509:alpha-Fetoproteins; D004964:Estriol