An enzyme immunoassay for the quantitative in vitro diagnostic measurement of active free 17 hydroxyprogesterone in saliva.
Measurements of 17-hydroxyprogesterone are used as an aid in the diagnosis of various disorders of the adrenal glands or the ovaries, and as an aid in the diagnosis of late onset of 21-hydroxylase deficiency, a common cause of Congenital Adrenal Hyperplasia.
This test is not intended for newborn screening.
Summary and Explanation
The steroid 17-Alpha-Hydroxyprogesterone (17-Alpha-OHP) is produced by both the adrenal cortex and gonads. Even though 17-Alpha-OHP has relatively little progestational activity, it is of intense clinical interest because it is the immediate precursor to 11-desoxycortisol (Cpd-S). Because Cpd-S is produced by 21-hydroxylation of 17-Alpha-OHP, measurement of 17-Alpha-OHP is a useful indirect indicator of 21-hydroxylase activity. In congenital 21-hydroxylase deficiency, the most common variety of Congenital Adrenal Hyperplasia (CAH), 17-Alpha-OHP is secreted in abundant excess. It is moderately elevated in the 11-Beta-hydroxylase deficiency as well. Measurement of 17-Alpha-OHP is therefore valuable in the initial diagnosis of CAH.
Adult non-pregnant women:
In adult non-pregnant women in the childbearing age group, 17-Alpha-OHP concentrations vary over the menstrual cycle with luteal phase concentrations being higher than follicular phase concentrations. This is because 17-Alpha-OHP is secreted parallel with progesterone from maturing follicles or from the corpus luteum. There is also a diurnal variation of 17-Alpha-OHP concentrations.
This rhythm is parallel with adrenal cortisol secretion such that maximum 17-Alpha-OHP concentrations are measured in samples obtained in the morning.
Congenital adrenal hyperplasia:
The principal application of the 17-Alpha-OHP is in the diagnosis of CAH in newborns with ambiguous genitalia and in virilized adolescent girls. Since 17-Alpha-OHP is the immediate precursor to 11-desoxycortisol, basal 17 Alpha-OHP concentrations are sharply elevated in patients with 21-hydroxylase deficiency and to a lesser degree in patients with 11-hydroxylase deficiency.
Because 17-Alpha-OHP concentrations are so markedly elevated in newborns and adolescent girls afflicted with CAH, a single basal measurement is all that is normally required to make the diagnosis.
Late onset adrenal hyperplasia:
More recently, 17-Alpha-OHP concentrations have been utilized in the evaluation of androgenized women where late onset 21-hydroxylase is suspected. This condition is clinically very subtle and since the presentation is the same as classical polycystic ovarian disease, basal plasma 17-Alpha-OHP concentrations, unlike classical congenital adrenal hyperplasia, are normal. The diagnosis is made by administration of an ACTH stimulation test.
PRINCIPLE OF THE TEST
The DRG Salivary 17Alpha-OHP 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 antibody (rabbit) directed towards an antigenic site on the 17Alpha-OHP molecule. Endogenous 17Alpha-OHP of a patient sample competes with a 17Alpha-OHP-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 17Alpha-OHP in the sample. After addition of the substrate solution, the intensity of colour developed is inversely proportional to the concentration of 17Alpha-OHP in the patient sample.