Estrogen is a hormone that is found in three types, estrone, estradiol and estriol. Urinary estrogen test is done to monitor and asses the fetus during pregnancy. Estrogen especially estriol levels are known to have increased levels in the 24 hour urine during pregnancy or during the 9 month course of pregnancy.
This test can also be ordered when a patient is experiencing infertility or when taking a hormone replacement therapy to check for the effectiveness of the treatment.
Kober reaction is the primary assay for urinary estrogen. In this assay the urine is heated in a strong aqueous sulfuric acid solution containing hydroquinone.
Before analysis the sample must be checked for glucose concentration. High levels of glucose can affect the reaction and can form acetaldehyde when reacted to hydroquinone thus giving false negative results. Hydrolysis of estrogen is accomplished by either adding HCl, heat or enzymatically. Ethyl acetate extraction separates the steroid hormones from other materials.
After hydrolysis and exclusion of the other urine materials, a combination of hydroquinone and sulfuric acid is added to the tube containing the estrogens. The tube is then heated to turn out a reddish-brown color solution. Absorbance is then determined spectrophotometry at 474, 512 and 556 nanometers. Followed by an Allen correction to estimate the estrogen concentration using standard solutions for calibration.
This assay is only relevant during the middle and latter stages of pregnancy or during the 15th to 20th week of gestation. Flourometric assays have a high sensitivity and accuracy for cases of non pregnancy.
Can cause false negative results:
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Can cause false positive results:
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Clinical chemistry, A fundamental textbook by Donald F. Calbreath