Free Estriol ELISA Kit


Human free estriol ELISA kit is a reliable quantitative procedure for measuring unconjugated estriol (free estriol, E3, oestriol) in human serum samples. This assay has a minimum sensitivity detection limit of 0.075 ng/ml.


Estriol (referred to as E3 or oestriol) is produced by the fetoplacental unit during pregnancy and it represent the predominant estrogen being formed. It has a half-life of approx. 20-30 minutes within the maternal bloodstream. The unconjugated form is able to pass via the placenta into the maternal circulation, where it undergoes a rapid conversion into sulfate derivatives and glucuronide in order to facilitate its excretion. The determination of the concentration has been helpful in evaluating the current fetal state.

Bodily fluids have been routinely measured for E3 in order to monitor and manage fetal well-being, particularly for high risk pregnant patients. There are also many advantages for measuring unconjugated E3 instead of total serum or urinary E3. Unconjugated E3 reflects more accurately the fetal outcome in diabetic pregnancies, its levels are not altered following certain antibiotics administration and the concentrations are free from effects which can be related to maternal hepatic or renal diseases.


All reagents supplied need to be stored at 2 °C – 8 °C, unopened reagents will retain reactivity until expiration date. Do not use reagents beyond this date.

  • Microtiterwells 12 x 8 (break apart) strips: Wells coated with an anti-Estriol antibody (polyclonal).
  • Standard 0-5: Concentration 0, 0.3, 1.2, 4.0, 15, 40 ng/mL.
  • Enzyme Conjugate.
  • Substrate Solution: Tetramethylbenzidine (TMB).
  • Stop Solution: Contains 0.5 M H2SO4, Avoid contact with the stop solution. It may cause skin irritations and burns.
  • Wash Solution (40x Concentrated).


The minimum sensitivity detection limit of human unconjugated estriol (free estriol) using current free estriol ELISA kit was approximately 0.075 ng/ml. The dynamic range for this assay is 0.3 – 40.0 ng/ml.


– Assay Dynamic Range: 0 – 40 ng/ml
– Specificity (Cross Reactivity): Highly specific for estriol (E3), does not cross react with -testosterone, estradiol (E2), estrone (E1) and cortisol.
– Analytical Sensitivity: 0.075 ng/ml
– Intra-Assay Variability: 3.01 – 4.66%
– Inter-Assay Variability: 4.59 – 9.49%
– Recovery: 89.0 – 112.3%
– Linearity: 86.3 – 107.9%
– Interfering Substances: None
– High-Dose-Hook Effect: No hook effect was detected
– Drug Interferences: None


  1. Very low maternal serum unconjugated estriol and prenatal diagnosis of steroid sulfatase deficiency. Fetal Diagn Ther. (1995) 10 (2): 76-9. David M., et al.
  2. Estrogens and the human male. Annu Rev Med. 1(976) 27: 357-70. Review. Marcus R. and Korenman S.G.
  3. Method comparison studies for prostate specific antigen and unconjugated estriol immunoassays. Clin Lab Sci. (2003) 16 (2): 94-8. Koenn M.E. and Ndah B.V.
  4. Molecular and kinetic basis for the mixed agonist/antagonist activity of estriol. Mol Endocrinol. (1997) 11 (12): 1868-78. Melamed M., et al.


  • Full Name: Free Estriol ELISA Kit
  • Reactivity: Human
  • Sample Type: Serum
  • Sensitivity: 0.075 ng/ml


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