Recent articles by
Cuckle et al., Canick et al., and Isozaki et al.
have evaluated urine -core fragment as a screening test for Down syndrome in second-trimester pregnancies. They found over four-fold elevation of -core fragment levels in Down syndrome pregnancies, and between 62 and 88 per cent detection of this trisomy at a 5 per cent false-positive rate. Urine -core fragment may be a superior screening test for Down syndrome pregnancies. In the present study, urinary total oestriol has been evaluated as a marker to use in combination with -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 ratio of -core fragment to total oestriol levels (creatinine-independent). -core fragment and total oestriol levels were determined (normalized to creatinine, ng/mg creatinine) in urine samples from 480 unaffected and 12 Down syndrome pregnancies, collected consecutively at a single prenatal diagnosis centre. The median -core fragment level in Down syndrome cases was 4•5 MOM. Fifty-eight per cent of Down syndrome cases had -core fragment levels exceeding the 95th centile of unaffected pregnancies. The median total oestriol level in Down syndrome cases was 0•33 MOM. Forty-two per cent of Down syndrome cases had total oestriol levels exceeding the 95th centile of unaffected pregnancies. We investigated the ratio of the two determinants ( -core fragment, ng/ml÷total oestriol, ng/ml) in our sample set. The median -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. Total oestriol complements -core fragment in urine screening for Down syndrome pregnancies. A test measuring the ratio of the two urine determinants may be a significant improvement over current serum methods for detecting Down syndrome. 1997 by John Wiley & Sons, Ltd.