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Lab Manual for UCSF Clinical Laboratories

Lab Manual for SFGH

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Item Value
Available Stat? No
Test code CORT
Performed by? Chemistry
Sendout? no
Price range $$$
In House Availability Monday - Friday
Saturday & Sunday (12 pm - 8 pm)
Principle The Siemens Centaur assay is a competitive immunoassay using a direct chemiluminescent technology.
Interpretation Serum or plasma cortisol is most frequently ordered in the setting of dynamic testing (stimulation or suppression protocols) to evaluate suspected adrenal insufficiency, corticosteroid excess (Cushing's syndrome) or congenital adrenal hyperplasia. The interpretation of random cortisol measurements, as well as of diurnal cortisol variation testing (e.g. 8 am and 4 pm draws) may be complicated by the many factors affecting secretion and metabolism of adrenal steroids. These include hepatic, renal and thyroid disease, nutrition, drugs, acute stress from trauma or illness, and in addition, the interference of some exogenous steroids with the assay used for measurement (see Interferences below).

Consult the Endocrine fellow regarding protocols for and interpretation of Cosyntropin¨ stimulations tests.
Container type gel tube (gold or green top)
Amount to Collect 2 mL
Collection Instructions citrated plasma (blue top tube) is not acceptable.
Sample type Blood
Special instructions Because of the diurnal variation of cortisol, basal cortisol levels should be obtained between 8 am and 9 am; otherwise, record the time of sampling on the requisition.
Normal range
4.3 – 22.4 mcg/dL (119-618 nmol/L) 7 am to 9 am
3.1 – 16.7 mcg/dL (86-461 nmol/L) 3 pm to 5 pm

Stability 2 days at 2-8°C. One month at -20°C.
Interferences 1. This method shows a high cross reactivity for prednisolone, prednisone, and 6-methyl-predinsolone, and therefore samples from patients receiving these drugs should not be run.

2. Estrogens, (e.g., oral contraceptives), will cause elevated cortisol levels. When estrogen therapy is discontinued, cortisol levels will fall to normal within two (2) weeks.

3. Auto- (rheumatoid factor) and heterophile antibodies in human serum can react with reagent immunoglobulins, interfering with in vitro immunoassays. Patients routinely exposed to animals or to animal serum products can be prone to this interference. Anomalous values, spuriously low or high, may be observed. Results inconsistent with clinical findings or previous laboratory values can be investigated by the laboratory for this phenomenon. Call the Clinical Chemistry Laboratory Medicine Resident (x65527, pager 415-443-2311).
References 1. Cartwright, G.E. and Wintrobe, M.M.: Am J Clin Nutr. 14:224, 1964.

2. Bayer 111808 Rev. E, 5/2000. Siemens Medical Solutions Diagnostics, Malvern, PA.

3. Nay, R. L.: Disorders of the Adrenal Gland. The Practice and principles of Medicine, Ed. AM Harvey, 11:797-808, 1984.

4. Orsulak, P.J.; Rush, A.J.: The Dexamethasone Suppression Test in Depression. J. Clin. Immunoassay, 6:302-7, 1983.
CPT coding 82533
Last Updated 10/16/2012 7:35:58 PM
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