SCREENING FOR DOWN-SYNDROME PREGNANCY USING BETA-CORE FRAGMENT - PROSPECTIVE-STUDY

Two recent publications by Cuckle et at, and one each by Canick et al. and Kellner et al., describe the use of urine beta-core fragment meas urements as a screening test for Down syndrome pregnancies. Median lev els of over 5.4 MOM were reported for cases of Down syndrome, with an over 72 per cent detection rate for a 5 per cent false-positive rate. Urine beta-core fragment was suggested as a superior screening test fo r Down syndrome pregnancies. These four studies were retrospectives, w ith samples from affected cases collected at different sites from thos e from normal cases. In the present study, prospective data were colle cted for 726 pregnancies over a 9-month period at a single medical cen tre. Fresh samples were assayed continuously, without knowledge of the karyotype. Urinary beta-core fragment levels in 709 unaffected sample s continually declined from 12 to 24 weeks of pregnancy. A logarithmic fit was optimal for the median curve. The log standard deviation of u naffected samples was 0.368. All 13 Down syndrome cases had levels exc eeding 1.0 MOM, with a median value of 4.1 MOM. Eight of 13 Down syndr ome cases (62 per cent) had levels exceeding the 95th centile. Results have not been adjusted for maternal age, which may improve the detect ion rate. The results reported here, while less impressive than those reported previously, confirm the usefulness of urine beta-core fragmen t as a screening test for Down syndrome. Because of the prospective na ture of this study, the 62 per cent sensitivity suggested here might b e more representative of the true performance of urinary beta-core fra gment in clinical practice than the higher rates observed in previous studies. Results for this single urine test are similar to those for t riple screen and other serum combination tests. Single analyte urine b eta-core fragment tests, or beta-core fragment combination protocols, may eventually replace serum analytes in screening for Down syndrome p regnancies. (C) 1997 by John Wiley & Sons, Ltd.