title: Efficacy of the genetic sonogram in a stepwise sequential protocol for down syndrome screening.
abstract: OBJECTIVE
  The purpose of this study was to evaluate the efficacy of the genetic sonogram in Down syndrome screening for women who have received the stepwise sequential test.
  
  
  METHODS
  This retrospective cohort study included women with singleton pregnancies who underwent stepwise sequential (first-trimester combined and second-trimester serum) screening and then had a genetic sonogram between March 2005 and January 2010. Stepwise sequential Down syndrome risks were multiplied by either a positive or negative likelihood ratio based on the second-trimester sonographic findings to determine the final Down syndrome risk. A final Down syndrome risk of 1:270 or higher was considered screen positive.
  
  
  RESULTS
  A total of 6286 women fulfilled our criteria, including 17 with Down syndrome-affected fetuses. After stepwise sequential testing, the Down syndrome detection rate was 88.2% (15 of 17), and after the genetic sonogram, there was a non-significant reduction in detection to 82.4% (14 of 17; P > .05). For the 6269 unaffected pregnancies, the genetic sonogram converted 58 screen-negative results (1%) to positive and 183 screen-positive results (3.1%) to negative. The net effect was a change in the false-positive rate from 6.2% (390 of 6269) after stepwise sequential screening to 4.2% (266 of 6269) after the genetic sonogram.
  
  
  CONCLUSIONS
  The genetic sonogram should be applied cautiously for women who have received prior prenatal screening tests. Women with screen-positive results need to be counseled that a negative sonographic result can be falsely reassuring. Conversely, for women with screen-negative results who have a risk close to the cutoff, a sonographic examination could assist in the decision of whether to accept or reject amniocentesis.
authors: Department of Obstetrics and Gynecology, University of Connecticut Health Center, Farmington, Connecticut USA. alirezashamshirsaz@yahoo.com
authors: Alireza A
authors: AA
authors: Shamshirsaz
authors: Samadh F
authors: SF
authors: Ravangard
authors: Garry
authors: G
authors: Turner
authors: Adam
authors: A
authors: Borgida
authors: Mary Beth
authors: MB
authors: Janicki
authors: Winston A
authors: WA
authors: Campbell
authors: Carolyn
authors: C
authors: Zelop
authors: Amirhoushang A
authors: AA
authors: Shamshirsaz
authors: Melissa
authors: M
authors: Spiel
authors: Anne Marie
authors: AM
authors: Prabulos
authors: Deborah
authors: D
authors: Feldman
authors: John
authors: J
authors: Rodis
authors: Charles J
authors: CJ
authors: Ingardia
authors: Padmalatha
authors: P
authors: Gurram
authors: Kisti
authors: K
authors: Fuller
authors: Yu M
authors: YM
authors: Fang
authors: Peter
authors: P
authors: Benn
authors: James F X
authors: JF
authors: Egan
mesh_terms: D015331:Cohort Studies; D003237:Connecticut / Q000453:epidemiology; D004314:Down Syndrome / Q000000981:diagnostic imaging* / Q000453:epidemiology*; D005260:Female; D020022:Genetic Predisposition to Disease / Q000453:epidemiology / Q000235:genetics; D006801:Humans; D008297:Male; D008403:Mass Screening / Q000379:methods* / Q000706:statistics & numerical data*; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D015995:Prevalence; D012189:Retrospective Studies; D012307:Risk Factors; D016216:Ultrasonography, Prenatal / Q000379:methods* / Q000706:statistics & numerical data*
keywords: Down syndrome screening; aneuploidy; antenatal screening; genetic sonogram; stepwise sequential