title: Combined first trimester nuchal translucency and second trimester biochemical screening tests among normal pregnancies.
abstract: We prospectively examined whether first trimester nuchal translucency (NT) and second trimester triple test (TT) results are correlated, and determined overlapping and mutual screen-positive rates. Results of NT, TT, amniocentesis and pregnancy outcome were obtained in 508 normal pregnancies. Inter-test correlation was performed by comparing the likelihood ratios (LR). Overlapping of screen-positive cases, of NT and TT, was determined by comparing mutual risks for Down syndrome (DS) livebirth of > or = 1:380. Combined screen-positive rates were evaluated by using summation risk (NT and/or TT exhibiting a risk > or = 1:380) and calculated risk (new risk > or / =1:380, based on multiplication of LR(NT) and LR(TT)). Screen-positive rates between NT and TT differed significantly and when either test showed an increased risk for DS, the probability of the other to predict the same was negligible (p<0.001). Overall screen-positive rates, at a risk > or = 1:380, were 2% and 5.7% for NT and TT, respectively. Summation and calculated combining methods were associated with 7.5% and 2.0% screen-positive rates, respectively. Amniocentesis was performed on 20.7% of the cases, mostly screen-negative ones. Our results showed that, in normal pregnancies, NT and TT do not correlate and that their combined calculated risk in normal pregnancies is associated with a low screen-positive rate of 2.0%.
authors.affiliation: Department of Obstetrics and Gynecology, Assaf Harofeh Medical Center, Zerifin, Sackler Faculty of Medicine, Tel Aviv University, Israel. aherman@asaf.health.gov.il
authors.forename: A
authors.initials: A
authors.lastname: Herman
authors.forename: Z
authors.initials: Z
authors.lastname: Weinraub
authors.forename: E
authors.initials: E
authors.lastname: Dreazen
authors.forename: S
authors.initials: S
authors.lastname: Arieli
authors.forename: S
authors.initials: S
authors.lastname: Rozansky
authors.forename: I
authors.initials: I
authors.lastname: Bukovsky
authors.forename: R
authors.initials: R
authors.lastname: Maymon
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000097:blood*; D004314:Down Syndrome / Q000175:diagnosis*; D005260:Female; D005315:Fetal Diseases / Q000175:diagnosis*; D006801:Humans; D008403:Mass Screening / Q000379:methods*; D011237:Predictive Value of Tests; D011247:Pregnancy; D011256:Pregnancy Outcome; D011261:Pregnancy Trimester, First; D011262:Pregnancy Trimester, Second; D011296:Prenatal Diagnosis; D011446:Prospective Studies; D016216:Ultrasonography, Prenatal
chemical_list: D015415:Biomarkers