A SENSITIVE ENZYME-IMMUNOASSAY FOR PREGNANCY-ASSOCIATED PLASMA-PROTEIN-A (PAPP-A) - A POSSIBLE FIRST TRIMESTER METHOD OF SCREENING FOR DOWN-SYNDROME AND OTHER TRISOMIES
Na. Bersinger et al., A SENSITIVE ENZYME-IMMUNOASSAY FOR PREGNANCY-ASSOCIATED PLASMA-PROTEIN-A (PAPP-A) - A POSSIBLE FIRST TRIMESTER METHOD OF SCREENING FOR DOWN-SYNDROME AND OTHER TRISOMIES, Archives of gynecology and obstetrics, 256(4), 1995, pp. 185-192
Pregnancy-associated plasma protein A (PAPP-A) is a large glycoprotein
produced mainly by the trophoblast during pregnancy and released into
the maternal circulation. Its biological function is unknown. In the
second trimester i.e. when Down syndrome (DS) screening is routinely p
erformed, the level of maternal serum PAPP-A was found to be within th
e normal range in pregnancies affected by fetal trisomy 21. However, P
APP-A was shown to be a potent marker for DS before 14 weeks of gestat
ion. Only radioimmunoassays (RIAs) based on labelled antigen competiti
on reached the required sensitivity for early pregnancy PAPP-A determi
nations; but they have a very short shelf life due to inherent tracer
half-life and, in the case of PAPP-A, instability of the labelled anti
gen after three weeks. We describe a convenient and novel enzyme immun
oassay (ELISA) with high sensitivity and a long shelf life.