Combined first trimester nuchal translucency and second trimester biochemical screening tests among normal pregnancies

✍ Scribed by A. Herman; Z. Weinraub; E. Dreazen; S. Arieli; S. Rozansky; I. Bukovsky; R. Maymon

• Publisher: John Wiley and Sons
• Year: 2000
• Tongue: English
• Weight: 80 KB
• Volume: 20
• Category: Article
• ISSN: 0197-3851
• DOI: 10.1002/1097-0223(200010)20:10<781::aid-pd908>3.0.co;2-z

✦ Synopsis

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%.