Obstetrics & Gynecology
REVIEWS
EFFECT OF STUDY DESIGN ON THE ASSOCIATION BETWEEN NUCHAL TRANSLUCENCY MEASUREMENT AND DOWN SYNDROME
Mol, Ben W. J. MD, PhD; Lijmer, Jeroen G. MD; van der Meulen, Jan MD, PhD; Pajkrt, Eva MD, PhD; Bilardo, Caterina M. MD, PhD; Bossuyt, Patrick M. M. PhD
Departments of Clinical Epidemiology and Biostatistics and Obstetrics and Gynecology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
Ben W. J. Mol, MD, Department of Clinical Epidemiology and Biostatistics, Academic Medical Center, University of Amsterdam, PO Box 22700, Amsterdam, 1100 DE, The Netherlands; E-mail: [email protected]
Received December 14, 1998. Received in revised form June 3, 1999. Accepted June 10, 1999.
Abstract
Objective
To evaluate the effect of verification bias on the accuracy of first-trimester nuchal translucency measurement for Down syndrome detection.
Methods
We used MEDLINE and EMBASE to identify all papers relating the results of nuchal translucency measurement to fetal karyotype. The detected studies were scored for verification bias. Fifteen studies without and ten with verification bias were included.
Results
Sensitivity and specificity were calculated for each study. For studies with verification bias, adjusted estimates of the sensitivity were calculated assuming a fetal loss rate for Down syndrome pregnancies of 48%. The sample size weighted sensitivity was 55% in studies without and 77% in those with verification bias, for specificities of 96% and 97%, respectively. After adjustment for verification bias, the sample size weighted sensitivity changed from 77% to 63%.
Conclusion
Studies with verification bias reported higher sensitivities, but also slightly higher specificities of nuchal translucency measurement than studies without verification bias. The difference in sensitivity is greater than could be explained by verification bias. We postulate that the experience of the sonographist might be an explanation for the differences.