hCG and the free β-subunit as screening tests for Down syndrome

✍ Scribed by George J. Knight; Glenn E. Palomaki; Louis M. Neveux; Karen K. Fodor; James E. Haddow

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 99 KB
• Volume: 18
• Category: Article
• ISSN: 0197-3851
• DOI: 10.1002/(sici)1097-0223(199803)18:3<235::aid-pd248>3.0.co;2-a

✦ Synopsis

Published studies have reached varying conclusions as to the benefit of replacing human chorionic gonadotropin (hCG) measurements with the free -subunit of hCG (the free -subunit) for Down syndrome screening. One study reports 14 per cent higher detection for the free -subunit, while another finds an actual loss in detection. To explore this issue further, we directly compared the screening performance of hCG and the free -subunit, alone and in combination with other serum markers, using banked sera obtained prior to amniocentesis and karyotyping. Altogether, 52 Down syndrome and 5065 unaffected pregnancies were studied. Sera were thawed and assayed for hCG and the free -subunit over 1 year. At a 5 per cent false-positive rate, the detection rate for hCG in combination with maternal age and alpha-fetoprotein was higher than when the free -subunit was substituted (62 versus 57 per cent). Ultrasound dating and adding unconjugated oestriol both increased detection. The present findings, along with those from six case-control studies (our re-analysis), indicate that the screening performances of hCG and the free -subunit are similar (median change in detection 0, range 8 to +3 per cent). Under optimal sample collection and transportation conditions, laboratories can expect to achieve similar screening performance using either hCG or the free -subunit measurements.