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Diagnostic Salivary Cortisol EIA Kit

Product:

AM/PM Salivary Cortisol Enzyme Immunoassay

Intended Use:

Quantitative measurement of salivary Cortisol

FDA:

510(k) FDA Approved 

Catalog Number:

631

Method: 

Enzyme Immunoassay (EIA), Colormetric

AMR:

0.1 ng/mL – 30 ng/mL

LOD:

0.05 ng/mL

Sample Size:

25 µL

Incubation:

1hr @ Room Temperature

# of tests: 

96 wells

Reading:

450nm

Storage:

2° - 8°C 

Shelf Life:

16 Months 

Assay Background:


In 1966, Katz and Shannon (1,2,3) using the Porter-Silber method were able to determine corticosteroid concentrations in saliva and were able to show that concentrations of corticosteroids in saliva, were related to blood concentrations. The advent of immunoassay made it possible to measure minute amounts of steroid hormones in blood. Subsequent modification of those assays allowed their measurement in saliva as well. These early assays, however, lacked validity due to matrix differences between serum and saliva, poor sensitivity and cumbersome extraction methods. Recently, several papers have been published on the determination of salivary Cortisol under varying physiological conditions using more specific and sensitive EIA and ELISA methods (18,20).

Cortisol (hydrocortisone, compound F) is the principle glucocorticoid secreted by the adrenal cortex. Adrenal secretion of cortisol is modulated by a complex negative feedback mechanism involving the central nervous system, hypothalamus, pituitary and adrenals. ACTH released from the pituitary augment’s adrenal secretion of cortisol. In turn, increased levels of cortisol suppress pituitary secretion of ACTH while falling levels of cortisol are associated with rising levels of ACTH. Normally there is diurnal variation of cortisol with highest values measurable in the morning samples and lowest values obtained in the late afternoon. Cortisol levels rise independently of this circadian rhythm in response to stress or depression. Increased cortisol production is associated with Cushing’s Syndrome and adrenal tumors while decreased production of cortisol is associated with adrenal insufficiency (Addison’s disease) and adrenocorticotropic hormone (ACTH) deficiency (21, 22, 23, 24).

In blood 90% of the circulating cortisol is firmly bound to cortisol binding globulin (CBG), 7% is weakly bound to albumin and only 1-3% is free or unbound. In saliva the majority of cortisol occurs in the free or unbound form and enters the saliva via intracellular mechanisms (25). Numerous studies consistently report a high correlation between serum and saliva cortisol indicating that salivary cortisol levels clinically confirm levels of cortisol in serum (26, 27, 28).




Assay Principle:


Cortisol calibrators and amounts of Cortisol-enzyme conjugate compete for binding sites on the antiserum. Cortisol from saliva or calibrators reduces Cortisol-enzyme conjugate from binding to the anti-cortisol. The basis of Enzyme immunoassay (EIA) is the quantitative relation between ligand concentration and proportion of cortisol-enzyme conjugate bound to antiserum. Concentration of samples and controls are interpolated from the calibration curve.




Assay Protocol


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