Do race-specific definitions of short long bones improve the detection of down syndrome on second-trimester genetic sonograms?
OBJECTIVE
The purpose of this study was to determine whether the use of race-specific definitions of short femur and humerus lengths improves Down syndrome detection.


METHODS
This was a retrospective cohort study over 16 years. For each self-reported maternal race (white, African American, Hispanic, and Asian), we evaluated the efficiency of Down syndrome detection using published race-specific formulas compared with a standard formula for short femur and humerus lengths (observed versus expected lengths < or =0.91 and < or =0.89, respectively). The sensitivity, specificity, and 95% confidence intervals for each parameter were compared. Screening performance was compared by areas under the receiver operating characteristic curves.


RESULTS
Of 58,710 women, 209 (0.3%) had a diagnosis of a fetus with Down syndrome. Although the race-based formula increased sensitivity in each population, the increase was statistically significant only in the white population, whereas a decrease in specificity was statistically significant in all 4 populations, as denoted by nonoverlapping confidence intervals. The area under the receiver operating characteristic curve for the model using the race-specific definition of short femur length was 0.67 versus 0.65 compared with the standard definition, and for humerus length it was 0.70 versus 0.71.


CONCLUSIONS
The use of race-based formulas for the determination of short femur and humerus lengths did not significantly improve the detection rates for Down syndrome.
Harper
Lorie M
LM
Department of Obstetrics and Gynecology, Washington University, 660 S Euclid, Campus Box 8064, St Louis, MO 63110 USA. harperl@wudosis.wustl.edu
Gray
Diana
D
Dicke
Jeffrey
J
Stamilio
David M
DM
Macones
George A
GA
Odibo
Anthony O
AO
D000328:Adult; D015331:Cohort Studies; D004314:Down Syndrome / Q000000981:diagnostic imaging* / Q000208:ethnology* / Q000235:genetics; D005260:Female; D005269:Femur / Q000002:abnormalities / Q000000981:diagnostic imaging* / Q000196:embryology; D006801:Humans; D006811:Humerus / Q000002:abnormalities / Q000000981:diagnostic imaging* / Q000196:embryology; D008923:Missouri / Q000208:ethnology; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D044469:Racial Groups / Q000706:statistics & numerical data*; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D016216:Ultrasonography, Prenatal / Q000379:methods / Q000706:statistics & numerical data*; D055815:Young Adult