MicroELISA

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The EIAgen Free Estriol Kit has been designed for the quantitative determination of Free Estriol (unconjugated estriol / u-E3) Concentration in Human Serum or Plasma.

The last few years have seen the development of screening for fetal Down Syndrome by measurement of multiple markers in maternal blood ⁽¹⁾. Although amniocentesis has been widely available for more than 40 years it can only be selectively used to diagnose the disorder because of the hazard to fetus. Of most employed for differential diagnosis the commonly used procedures are AFP, hCG, free beta-HCG and unconjugated estriol.⁽²⁾

Unconjugated estriol in the serum of pregnant women originates almost exclusively from precursors in the fetus, via the placenta.⁽³⁾ The clinical evidence shows that in uncomplicated pregnancies, the production of estriol increases steadily throughout the last trimester; however, in pregnancies complicated by placental insufficiency the synthesis of estriol decreases rapidly. For many years the most commonly used method for monitoring estriol synthesis (as an index to fetal stress) has been to measure estriol and estriol conjugates in a 24 hr urine sample⁽⁴⁾. However, changes in renal clearance and diurnal variations can make the results of these determinations suspect. In recent years investigators have found the determinations of unconjugated estriol in pregnancy plasma as an alternative to the urinary assay to be a better marker of fetal stress⁽⁶⁾. Abnormally low levels of estriol in a pregnant woman may indicate a problem with the development in the child. Levels of estriol in non-pregnant women do not change much after menopause, and levels are not significantly different from levels in men ^(7).

The EIAgen Free Estriol Kit uses a specific anti-estriol antibody, and does not require prior sample extraction of serum or plasma. Cross-reactivity to other naturally-occurring and structurally   related steroids is low.

The employment of several serum references of known Estriol concentration permits construction of a graph of activity and con­centration. From comparison to the dose response curve, an unknown specimen's activity can be correlated with Estriol concentration.

The essential reagents required for a enzyme immunoassay include antibody, enzyme-antigen conjugate and native antigen.

Upon mixing biotinylated antibody, enzyme-antigen conjugate and a serum containing the native antigen, a competition reaction results between the native antigen and the enzyme-antigen conjugate for a limited number of antibody binding sites.

A simultaneous reaction between the biotin attached to the antibody and the streptavidin immobilized on the microwell occurs. This effects the separation of the antibody bound fraction after decantation or aspiration. 

The enzyme activity in the antibody bound fraction is inversely proportional to the native antigen concentration. By utilizing several different serum references of known antigen con­centration, a dose response curve can be generated from which the anti­gen concentration of an unknown can be ascertained.

The kit contains reagents for 96 tests (code LI4046).

Bring reagents to room temperature before use.