Comparison of 12 assays for detecting hCG and related molecules in urine samples from Down syndrome pregnancies.
Urine is a new medium for Down syndrome testing. In an effort to determine the best type of human chorionic gonadotropin (hCG)-related immunoassay for urine testing, we examined 14 Down syndrome and 91 unaffected pregnancy urine samples with 12 established assays. The assays included (a) those that detect hCG beta-core fragment only; (b) those that detect beta-core fragment with less than 18 per cent free beta-subunit cross-reactivity; (c) that which equally detects free beta-subunit and beta-core fragment; and (d) those that detect hCG, free beta-subunit, or combinations thereof. The seven type a and b assays had the highest sensitivity for Down syndrome. The median MOM for Down syndrome was 5.93 (range 4.73-7.53). At a 10 per cent false-positive rate, the median observed detection rate was 93 per cent (range 79-100 per cent) and the median predicted detection rate was 85 per cent (range 69-96 per cent). The assays that did not mainly detect beta-core fragment (types c and d) had poorer screening performance. The median MOM for Down syndrome was 2.70 (range 2.16-3.63 MOM). At a 10 per cent false-positive rate, the median observed detection rate was 50 per cent (range 36-64 per cent) and the median predicted detection rate was 37 per cent (range 21-62 per cent). We infer that the assays that only detect beta-core fragment, or beta-core fragment with minor free beta-subunit cross-reactivity (types a and b), are the better urine-based tests for Down syndrome screening.
Cole
L A
LA
Department of Obstetrics and Gynecology, Yale University School of Medicine, New Haven, CT 06520, USA. laurence.cole@yale.edu
Kellner
L H
LH
Isozaki
T
T
Palomaki
G E
GE
Iles
R K
RK
Walker
R P
RP
Ozaki
M
M
Canick
J A
JA
D016022:Case-Control Studies; D006063:Chorionic Gonadotropin / Q000652:urine*; D018997:Chorionic Gonadotropin, beta Subunit, Human / Q000652:urine*; D004314:Down Syndrome / Q000175:diagnosis*; D005260:Female; D006801:Humans; D007118:Immunoassay; D011237:Predictive Value of Tests; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D011296:Prenatal Diagnosis / Q000379:methods*; D012680:Sensitivity and Specificity
D006063:Chorionic Gonadotropin; D018997:Chorionic Gonadotropin, beta Subunit, Human