R. Bahado-singh et al., Urine hyperglycosylated hCG plus ultrasound biometry for detection of Downsyndrome in the second trimester in a high-risk population, OBSTET GYN, 95(6), 2000, pp. 889-894
Objective: To evaluate measurement of levels of urine hyperglycosylated hCG
, a form of hCG with abnormally branched oligosaccharide side chains, in co
njunction with ultrasound biometry for Down syndrome risk prediction in an
at-risk group.
Method: We prospectively measured urine hyperglycosylated hCG levels, humer
al length, and nuchal thickness in women who had second-trimester amniocent
esis. Urine hyperglycosylated hCG levels were measured by a two-step enzyme
-immunometric assay using monoclonal antibody beta 152. Humeral length, nuc
hal thickness, and hyperglycosylated hCG values were expressed as multiples
of the median, and the Down syndrome screening efficiency of the three ana
lytes plus age was determined. A receiver operating characteristic (ROC) cu
rve was generated, and the area under the curve was used to assess the Down
syndrome screening performance of the algorithm.
Results: There were 23 cases of Down syndrome among 1016 singleton pregnanc
ies. Mean gestational age (+/- standard deviation) was 16.1 +/- 1.2 weeks a
t the time of amniocentesis. Mean maternal age was 37.1 +/- 3.2 years. Biom
etry and measurement of hyperglycosylated hCG levels had a 91.3% detection
rate at a 3.2% false-positive rate and a 100% detection rate at a 10.7% fal
se-positive rate. The area under the ROC curve was 0.986 (P < .001), and th
at for measurement of hyperglycosylated hCG levels plus age was 0.941 (P <
.001). The area under the curve was significantly larger with combined bioc
hemical and biometry markers compared with measurement of hyperglycosylated
hCG levels plus age alone (P < .02), proving that the former was superior
to the latter.
Conclusion: A new Down syndrome biochemical marker combined with ultrasound
biometry had a high screening efficiency in a high-risk group. All cases o
f Down syndrome in this study population would have been detected at an amn
iocentesis rate of less than 10.7%. Our results appear superior to those fo
und with other second-trimester algorithms. The combination is promising as
an alternative to "automatic" genetic amniocentesis in women of advanced m
aternal age and other high-risk groups. (Obstet Gynecol 2000;95:889-94. (C)
2000 by The American College of Obstetricians and Gynecologists).