TY - JOUR
T1 - The performance of second trimester long bone ratios for Down syndrome screening is influenced by gestational age
AU - Wang, Eileen
AU - Chen, Catherine
AU - Glimco, Elizabeth
AU - Grobman, William
PY - 2010/7
Y1 - 2010/7
N2 - Objective.To determine if gestational age (GA) at the time of ultrasound impacts the positive predictive value of shortened femur and humerus lengths (FL, HL) for trisomy 21 (T21). Methods.Sonograms from 14 to 21 and 6/7 weeks' gestation were collected over a 28 month period. Multiple gestations or fetuses with major structural anomalies were excluded. Biometric data and GA were obtained; the expected HL (or FL): observed HL (or FL) ratios were calculated using two regression formulas (Benacerraf and Nyberg). A HL ratio <0.90 and a FL ratio <0.91 were considered shortened. T21 fetuses were identified through database and chart review. Positive predictive values (PPV) for T21 of the shortened bone ratios were determined, then stratified by GA. Results.Of the 2606 ultrasounds, 8.9 and 18.9 of fetuses had shortened HL and FL ratios, respectively, using the Benacerraf formula. Shortened ratios were noted significantly less commonly (2.3 and 4.4, respectively, P<0.001 for each) using the Nyberg formula. With either formula, abnormal bone ratios were more frequently documented with a GA less than 17 weeks (P<0.001). There were 17 T21 pregnancies. Conclusions.GA and formula selection influence the performance of long bone ratios as soft markers for T21 in the second trimester.
AB - Objective.To determine if gestational age (GA) at the time of ultrasound impacts the positive predictive value of shortened femur and humerus lengths (FL, HL) for trisomy 21 (T21). Methods.Sonograms from 14 to 21 and 6/7 weeks' gestation were collected over a 28 month period. Multiple gestations or fetuses with major structural anomalies were excluded. Biometric data and GA were obtained; the expected HL (or FL): observed HL (or FL) ratios were calculated using two regression formulas (Benacerraf and Nyberg). A HL ratio <0.90 and a FL ratio <0.91 were considered shortened. T21 fetuses were identified through database and chart review. Positive predictive values (PPV) for T21 of the shortened bone ratios were determined, then stratified by GA. Results.Of the 2606 ultrasounds, 8.9 and 18.9 of fetuses had shortened HL and FL ratios, respectively, using the Benacerraf formula. Shortened ratios were noted significantly less commonly (2.3 and 4.4, respectively, P<0.001 for each) using the Nyberg formula. With either formula, abnormal bone ratios were more frequently documented with a GA less than 17 weeks (P<0.001). There were 17 T21 pregnancies. Conclusions.GA and formula selection influence the performance of long bone ratios as soft markers for T21 in the second trimester.
KW - Down syndrome screening
KW - Femur length
KW - Humerus length
KW - Second trimester
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U2 - 10.3109/14767050903287224
DO - 10.3109/14767050903287224
M3 - Article
C2 - 20540658
AN - SCOPUS:77953629111
SN - 1476-7058
VL - 23
SP - 642
EP - 645
JO - Journal of Maternal-Fetal and Neonatal Medicine
JF - Journal of Maternal-Fetal and Neonatal Medicine
IS - 7
ER -