The DRG Free Estriol ELISA is an enzyme immunoassay for the quantitativemeasurement of free estriol (unconjugated estriol) in serum during the second half of pregnancy.
Estriol (E3) is the major estrogen formed by the fetoplacental unit during pregnancy. Unconjugated E3 passes through the placenta into the maternal circulation, where it is rapidly converted into glucuronide and sulfate derivatives to facilitate its excretion. The half-life of estriol in the maternal bloodstream is only 20-30 minutes. Its measurement, therefore offers a convenient and quick evaluation of current fetal status. Plasma estriol levels increase steadily throughout pregnancy and most rapidly during the third trimester (28-40 weeks). A sudden decrease in fetoplacental E3 production will result in a rapid fall in unconjugated E3 in the maternal serum. There are several potential advantages to measuring unconjugated E3 rather than total serum or urinary E3. Unconjugated estriol levels are free from effects related to maternal renal or hepatic disease, and are not altered by the administration of certain antibiotics. Unconjugated E3 more accurately reflects fetal outcome in diabetic pregnancies – and since no hydrolysis of unconjugated E3 is required, a more rapid tumaround for the test result is possible.
The DRG Free Estriol ELISA Kit is a solid phase enzyme-linked immunosorbent assay (ELISA), based on the principle of competitive binding. The microtiter wells are coated with a polyclonal [rabbit] antibody directed towards an antigenic site on the Estriol molecule. Endogenous Estriol of a sample competes with an Estriol-horseradish peroxidase conjugate for binding to the coated antibody. After incubation the unbound conjugate is washed off. The amount of bound peroxidase conjugate is inversely proportional to the concentration of Estriol in the sample. After addition of the substrate solution, the intensity of color developed is inversely proportional to the concentration of Estriol in the sample.