title: Correlation and overlapping between nuchal translucency and triple test among Down syndrome-affected pregnancies.
abstract: 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.
authors.affiliation: 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
authors.forename: Arie
authors.initials: A
authors.lastname: Herman
authors.forename: Eliezer
authors.initials: E
authors.lastname: Dreazen
authors.forename: Yosef
authors.initials: Y
authors.lastname: Tovbin
authors.forename: Orit
authors.initials: O
authors.lastname: Reish
authors.forename: Ian
authors.initials: I
authors.lastname: Bukovsky
authors.forename: Ron
authors.initials: R
authors.lastname: Maymon
mesh_terms: 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
chemical_list: D006063:Chorionic Gonadotropin; D000509:alpha-Fetoproteins; D004964:Estriol