Free Estriol ELISA Kit

  • Created on the 15 February, 2017.


Human free estriol ELISA kit is a reliable quantitative procedure for measuring unconjugated estriol (free estriol) in human serum samples. This assay has a minimum sensitivity detection limit of 0.02 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, it is well known that the unconjugated form of E3 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 of free estriol (unconjugated E3) has been helpful in evaluating the current fetal state. In general there is an increase in plasma estriol levels throughout pregnancy, with the most rapid elevation during the third trimester. Therefore, if there was a sudden reduction in feto-placental E3 production then this would lead to a rapid fall in the levels of unconjugated E3 that is present in the maternal serum.

Bodily fluids have been routinely measured for estriol (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.

Due to the ranges for normal and abnormal serum conjugated E3 being relatively wide and overlap considerably, it is recommended that the patient is monitored frequently since a single E3 measurement will be of little value in order to establish any individual trend. The following ELISA assay uses a highly specific estriol antibody, together with the elimination of radioisotopes and the long shelf life of this product, this procedure has become applicable to both large and small laboratories.


Reagents which are supplied with the free estriol ELISA kit, please following instructions for storage conditions.
1. Microtiter Plate: polyclonal anti-Estriol antibody coated.
2. Standard (Standard 0-5): 0 – 0.3 – 1.2 – 4.0 – 15 – 40 ng/mL.
3. Control Low & High.
4. Enzyme Conjugate.
5. Substrate Solution.
6. Stop Solution.
7. Wash Solution.

Note: Additional Standard 0 for sample dilution is available upon request.


The minimum sensitivity detection limit of unconjugated estriol using current human free estriol ELISA kit was approximately 0.02 ng/ml. The dynamic range for this assay is 0.3 – 40.0 ng/ml.


  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: 0.02 ng/ml



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