Correlation and overlapping between nuchal translucency and triple test among Down syndrome-affected pregnancies.
OBJECTIVE
To examine the correlation and extent of overlapping between first-trimester nuchal translucency (NT) and second-trimester triple test (TT) results in Down syndrome (DS)-affected pregnancies.


METHODS
Results of both tests were obtained in 28 cases with DS. Inter-test correlation was performed by comparing the likelihood ratios (LRs). Screen-positive rates (risk >1:380) were calculated for different age groups by adjusting age-dependent background risk and tests' LRs. Overlapping referred to ratio between screen-positive cases by both tests simultaneously and total screen-positive cases by either one or both tests.


RESULTS
No correlation was found between the tests' LRs (Pearson correlation test, r = 0.0487). The overlapping between the tests was 25% and 38.5% among young patients of 20 and 35 years of age, respectively. The average overlapping among patients between 25 and 35 years of age was approximately 33%. Only 3 of the 28 DS cases demonstrated LRs <1 by both tests and moreover none exhibited LRs <0.2 by both tests.


CONCLUSIONS
The degree of overlapping of one third, between NT and TT, confirms the assumption that both tests utilized together improves DS detection. Screen- negative result, by both tests simultaneously, may reassure low-risk population and aid to reduce the number of non-indicated invasive tests.
Herman
Arie
A
Department of Obstetrics and Gynecology and Genetic Institute, Assaf Harofeh Medical Center, Zerifin, and Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel. aherman@asaf.health.gov.il
Dreazen
Eliezer
E
Tovbin
Yosef
Y
Reish
Orit
O
Bukovsky
Ian
I
Maymon
Ron
R
D000328:Adult; D000649:Amniocentesis; D006063:Chorionic Gonadotropin / Q000097:blood; D004314:Down Syndrome / Q000175:diagnosis* / Q000000981:diagnostic imaging*; D004964:Estriol / Q000097:blood; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D007621:Karyotyping; D016013:Likelihood Functions; D008297:Male; D008423:Maternal Age; D009333:Neck / Q000000981:diagnostic imaging; D011247:Pregnancy; D011296:Prenatal Diagnosis; D012307:Risk Factors; D016216:Ultrasonography, Prenatal; D000509:alpha-Fetoproteins / Q000032:analysis
D006063:Chorionic Gonadotropin; D000509:alpha-Fetoproteins; D004964:Estriol