COMBINING BETA-CORE FRAGMENT AND TOTAL ESTRIOL MEASUREMENTS TO TEST FOR DOWN-SYNDROME PREGNANCIES

Recent articles by Cuckle et al., Canick et al., and Isozaki et al. ha ve evaluated urine beta-core fragment as a screening test for Down syn drome in second-trimester pregnancies. They found over four-fold eleva tion of beta-core fragment levels in Down syndrome pregnancies, and be tween 62 and 88 per cent detection of this trisomy at a 5 per cent fal se-positive rate. Urine beta-core fragment may be a superior screening test for Down syndrome pregnancies. In the present study, urinary tot al oestriol has been evaluated as a marker to use in combination with beta-core fragment in screening for Down syndrome pregnancies. The two markers were evaluated separately in relation to the urine creatinine concentration. To amplify screening performance, we evaluated the rat io of beta-core fragment to total oestriol levels (creatinine-independ ent). beta-core fragment and total oestriol levels were determined (no rmalized to creatinine, ng/mg creatinine) in urine samples from 480 un affected and 12 Down syndrome pregnancies, collected consecutively at a single prenatal diagnosis centre. The median beta-core fragment leve l in Down syndrome cases was 4.5 MOM. Fifty-eight per cent of Down syn drome cases had beta-core fragment levels exceeding the 95th centile o f unaffected pregnancies. The median total oestriol level in Down synd rome cases was 0.33 MOM. Forty-two per cent of Down syndrome cases had total oestriol levels exceeding the 95th centile of unaffected pregna ncies, We investigated the ratio of the two determinants (beta-core fr agment, ng/ml divided by total oestriol, ng/ml) in our sample set, The median beta-core fragment:total oestriol ratio in Down syndrome cases was 13 MOM. Seventy-five per cent of Down syndrome cases had a ratio exceeding the 95th and the 99.5th centile of unaffected pregnancies. T otal oestriol complements beta-core fragment in urine screening for Do wn syndrome pregnancies. A test measuring the ratio of the two urine d eterminants may be a significant improvement over current serum method s for detecting Down syndrome. (C) 1997 by John Wiley & Sons, Ltd.