Medical Genetics If MSAFP alone is tested, 20 per cent of ds fetuses will test low If msafp and human chorionic gonadotrophin(HCg)are determined 50-60 % o of ds fetuses will be identified. If MsaFP Hcg and estradiol (E2) are tested, 60-70 of DS fetuses will be identified. Some HCG testing employs a beta subunit but this is not widespreadMedical Genetics If MSAFP alone is tested, 20 per cent of DS fetuses will test low. If MSAFP and human chorionic gonadotrophin (HCG) are determined, 50 - 60 % of DS fetuses will be identified. If MSAFP, HCG and estradiol (E2) are tested, 60 -70 % of DS fetuses will be identified. Some HCG testing employs a beta subunit but this is not widespread