Urinary hyperglycosylated hCG in first trimester screening for chromosomalabnormalities

Hyperglycosylated human chorionic gonadotrophin (H-hCG), also known as Inva sive Trophoblast Antigen or ITA, is a unique metabolic variant of hCG with more complex oligosaccharide side chains. Concentrations are independent of regular hCG. Urine H-hCG has recently proved to be a highly sensitive mark er for Down syndrome screening in the second trimester of pregnancy. We eva luated H-hCG as a potential marker in the first trimester of pregnancy. Mat ernal urine samples were collected from 10(+0) to 11(+6) weeks of gestation prior to genetic analysis and stored in frozen form. Samples from eight ca ses of Down syndrome, two cases of trisomy 13, one case of trisomy 18, and 55 control pregnancies were hand-carried frozen to the USA and tested blind ly. Samples were tested in a specific H-hCG immunoassay and values were nor malized to creatinine concentration. Values were plotted against gestationa l age, and multiples of control pregnancy median (MoM) calculated. The medi an level of the MoMs of the eight Down syndrome cases was 3.6 MoM. Five of the eight Down syndrome cases exceeded the 90th centile of the 55 unaffecte d cases. The MoMs of the trisomy 13 and 18 pregnancies were 0.2, 0.2 and 0. 3. All three cases were under the 10th centile of unaffected pregnancies. T he results of this study indicate that H-hCG testing may be useful in scree ning for Down syndrome in the first trimester of pregnancy. Further studies are needed to assess the potential screening values of urine H-hCG and the combination of this test with free P-subunit, PAPP-A and other markers for Down syndrome in the first trimester of pregnancy. Copyright (C) 2000 John Wiley & Sons, Ltd.