Indication-specific accuracy of second-trimester genetic ultrasonography for the detection of trisomy 21

• Published in: American journal of obstetrics and gynecology Vol. 181; no. 5; pp. 1045 - 1048
• Main Authors: Vintzileos, Anthony M., Guzman, Edwin R., Smulian, John C., Day-Salvatore, Debra L., Knuppel, Robert A.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Philadelphia, PA Mosby, Inc 01-11-1999; Elsevier
• Subjects: Accuracy of genetic ultrasonography; Adolescent; Adult; Amniocentesis; Biological and medical sciences; Chromosome Aberrations - diagnosis; Chromosome Aberrations - diagnostic imaging; Chromosome Aberrations - epidemiology; Chromosome Aberrations - genetics; Chromosome Disorders; Diseases of mother, fetus and pregnancy; Down Syndrome - diagnosis; Down Syndrome - diagnostic imaging; Down Syndrome - epidemiology; Down Syndrome - genetics; Female; Genetic Testing; Gestational Age; Gynecology. Andrology. Obstetrics; Humans; Maternal Age; Medical sciences; Middle Aged; Odds Ratio; Pilot Projects; Pregnancy; Pregnancy Trimester, Second - blood; Pregnancy Trimester, Second - genetics; Pregnancy, High-Risk; Pregnancy. Fetus. Placenta; Prevalence; Prospective Studies; Risk Factors; Sensitivity and Specificity; trisomy 21 risk adjustment; Ultrasonography, Prenatal; trisomy 21 risk adjustment; Accuracy of genetic ultrasonography; Chromosomal aberration; Sonography; Second trimester; Human; Trisomy; Chromosome G21; Aneuploidy; Prenatal; Sensitivity; Specificity; Echography; Predictive value; Diagnosis
• ISSN: 0002-9378; 1097-6868
• DOI: 10.1016/S0002-9378(99)70078-5

Objective: The object of this study was to determine whether there are any clinically significant indication-specific variations in the accuracy of second-trimester genetic ultrasonography and to provide a risk adjustment for fetal trisomy 21 according to the results of genetic ultrasonography.
Study Design: From November 1, 1992, to September 30, 1998, a second-trimester genetic sonogram was offered to all pregnant women who were at an increased risk for fetal trisomy 21 (≥1:274) because of either advanced maternal age (≥35 years) or abnormal serum biochemical profile or both of these. Outcome information included the results of genetic amniocentesis if performed and the results of pediatric assessment and follow-up after birth. In determining diagnostic accuracy of the genetic sonogram the presence of ≥1 abnormal ultrasonographic marker was considered an abnormal test result.
Results: A total of 1835 fetuses with known outcomes underwent genetic ultrasonography between 15 and 24 weeks’ gestation; of these 1792 had normal results, 34 had trisomy 21, and 9 had other chromosomal abnormalities. The likelihood of fetal trisomy 21 was reduced by 80% after a normal result of genetic ultrasonography. The overall sensitivity, specificity, and positive and negative predictive values of genetic ultrasonography for the detection of trisomy 21 were 82%, 91%, 15%, and 99.6%, respectively. There were no significant indication-specific variations in the accuracy of second-trimester ultrasonography. The sensitivity for the detection of fetal trisomy 21 ranged from 80% among women with advanced maternal age to 100% among women with both an abnormal biochemical profile and advanced maternal age.
Conclusions: The likelihood of fetal trisomy 21 risk was reduced 80% after a normal result of genetic ultrasonography. In addition there were no significant indication-specific variations in the detection rate of genetic ultrasonography. (Am J Obstet Gynecol 1999;181:1045-8.)