Maternal serum invasive trophoblast antigen and first-trimester Down syndrome screening.

Abstract

BACKGROUND:

In the United States, Down syndrome screening is still performed mainly in the second trimester, using 3 or 4 markers. Moving screening into the first trimester has the advantage of earlier diagnosis. Currently, first-trimester screening typically includes maternal serum pregnancy-associated plasma protein-A (PAPP-A), the free beta-subunit of human chorionic gonadotropin (free beta), and ultrasound measurement of nuchal translucency thickness (NT). The current report describes a case-control study of serum invasive trophoblast antigen (ITA) and its possible inclusion in first-trimester screening for Down syndrome.

METHODS:

As part of an earlier observational study, serum samples from 54 Down syndrome and 276 matched unaffected pregnancies were collected between 9 and 15 weeks of gestation. Samples had been aliquoted and stored at -20 degrees C for 8 years. ITA was measured and converted to weight-adjusted multiples of the median (MoM). The distributions of other first-trimester markers are from a single published study.

RESULTS:

Median ITA MoM in Down syndrome pregnancies increase as gestational age increases (2.02 MoM at 11 and 2.44 MoM at 13 completed weeks). At 75% detection, maternal age in combination with ITA and PAPP-A measurements have an 8.0% false-positive rate, slightly lower than the 8.8% found for the free beta and PAPP-A combination; adding NT measurements reduces false positives for the 2 combinations to 2.0% and 1.8%, respectively.

CONCLUSION:

Serum ITA appears to be a useful first-trimester Down syndrome marker that could replace free beta measurements while maintaining performance.

• Authors: Glenn E Palomaki, George J Knight, Louis M Neveux, Raj Pandian, James E Haddow
• Journal: Clinical chemistry (Clin Chem) Vol. 51 Issue 8 Pg. 1499-504 (Aug 2005) ISSN: 0009-9147 [Print] England
• PMID: 15961547 (Publication Type: Journal Article, Multicenter Study, Research Support, Non-U.S. Gov't)

Chemical References

• Biomarkers
• Chorionic Gonadotropin
• glycosylated HCG
• Pregnancy-Associated Plasma Protein-A

Topics

• Autoanalysis
• Biomarkers (blood)
• Case-Control Studies
• Chorionic Gonadotropin (blood)
• Down Syndrome (diagnosis)
• False Positive Reactions
• Female
• Glycosylation
• Humans
• Immunoassay
• Luminescent Measurements
• Mass Screening (methods)
• Pregnancy
• Pregnancy Trimester, First
• Pregnancy-Associated Plasma Protein-A (analysis)
• Trophoblasts (metabolism)