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Test Code CORT or LAB61 Cortisol, Serum or Plasma

Important Note

Patient Preparation: For 12 hours before this test do not take multivitamins or dietary supplements containing biotin (vitamin B7), which is commonly found in hair, skin, and nail supplements and multivitamins.   Biotin can interfere with many immunoassay tests.

Collection instructions: Morning (8 a.m.) and afternoon (4 p.m.) specimens are preferred. Please indicate the time of draw on the request form.

Specimen Requirements

Container Type:

Optimal: Gold or Mint*

*For STAT requests

Acceptable: Red or Green
Optimal Collection Volume: 

4.5mL; full tube
Minimum Volume:

1 mL whole blood
Collection Instructions:

Gently invert the sample 5-6 times after collection.
Specimen Transport:

Refrigerate
Processing Instructions: 

1. If serum, allow the specimen to clot for 30 minutes.

2. Centrifuge specimen within 2 hours of collection.

3. After centrifugation, specimen tubes without a gel barrier should have the serum or plasma aliquoted to a false bottom container.

4. Keep serum or plasma refrigerated until testing can be performed.

Specimen Stability

Specimen Type Temperature Time
Serum* Refrigerated 4 days
Room Temperature 24 hours
Frozen 12 months

*Note: Heparinized plasma in gel separator tubes is less stable than serum and is only suitable for add-on testing up to 2 days following sample collection.

Specimen Rejection Criteria

Hemolysis Mild OK; Moderate OK; Gross Reject
Lipemia Mild OK; Moderate OK; Gross Reject
Icterus Mild OK; Moderate OK; Gross Reject
Other Quantity not sufficient

Useful For

Used to diagnose the function of the adrenal gland, the pituitary, and the hypothalamus. Hyposecretion of cortisol (Addison’s disease) may be differentiated from hypersecretion of cortisol (Cushing’s Syndrome) by measurement of the cortisol level before and after administering ACTH or dexamethasone.

Methodology

Roche Cobas - Electrochemiluminescence assay

Reference Ranges

Note: Reference range revised on 1/31/2023 based upon consultation and review of historical data from Bronson, test manufacturer literature, and ranges published by other facilities using the same testing methodology.

 

Time Frame Reference Range and Reporting Units
6:00-10:00 AM 6.0-23.0 ug/dL
4:00-8:00 PM 2.7-12.0 ug/dL

A comment is appended to all results stating, "The reference range does not apply to patients receiving oral contraceptives, which increase serum cortisol levels."

Interpretive

The cortisol concentration in the serum or plasma normally shows a diurnal variation. The maximum level (up to 25 mg/dL) usually occurs early in the morning, then falls throughout the day to a 9 PM level, about one-half the 8 AM level. The cortisol level from 9 PM to about 4 AM is relatively constant.

 

Elevated levels are found during the newborn period. The cortisol concentration in serum attains adult values by the end of the first week of postnatal life and thereafter does not vary with age.

 

Day(s) Performed

24/7

Expected TAT

Same day

Performing Laboratory

Bronson Laboratory, Chemistry - Kalamazoo

Sample Retention Time

7 days

CPT Code

82533

LOINC Code

2143-6