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Efficacy of the Genetic Sonogram in a Stepwise Sequential Protocol for Down Syndrome Screening
Author(s) -
Shamshirsaz Alireza A.,
Ravangard Samadh F.,
Turner Garry,
Borgida Adam,
Janicki Mary Beth,
Campbell Winston A.,
Zelop Carolyn,
Shamshirsaz Amirhoushang A.,
Spiel Melissa,
Prabulos Anne Marie,
Feldman Deborah,
Rodis John,
Ingardia Charles J.,
Gurram Padmalatha,
Fuller Kisti,
Fang Yu M.,
Benn Peter,
Egan James F. X.
Publication year - 2013
Publication title -
journal of ultrasound in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.574
H-Index - 91
eISSN - 1550-9613
pISSN - 0278-4297
DOI - 10.7863/ultra.32.9.1607
Subject(s) - medicine , obstetrics , down syndrome , false positive rate , cohort , retrospective cohort study , prenatal diagnosis , singleton , fetus , pregnancy , second trimester , gynecology , genetics , mathematics , psychiatry , biology , statistics
Objectives 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.