| Laboratory: | Clinical Biochemistry (AUTOMATED) | |||||||||||||||||||
| Test Name: |
CORTISOL - (P) (S)
Test Code:
COR
|
|||||||||||||||||||
| Clinical Information: |
Description: Plasma cortisol testing is used to screen and diagnose primary and secondary adrenal insufficiency, as well as in differential diagnosis of Cushing syndrome.
Patient Preparation Instructions: Discontinue high dose biotin (and multivitamins) at least 8 hours prior to blood collection. |
|||||||||||||||||||
| Collection Devices: |
|
|||||||||||||||||||
| Specimen Required: |
Plasma: 2.0 mL
Pediatric Plasma: 0.2 mL
Collection Information: 1. Draw blood at indicated time: · AM cortisol specimens should be collected at 0700 - 0900h · PM cortisol specimens should be collected at 1500 - 1700h · All other collection times are considered random. 2. Centrifuge plasma/serum within one hour of collection. 3. Aliquot (if not tested onsite) Specimen Stability: Ambient: 24 hours Refrigerated: 4 days Frozen: 12 months, freeze only once |
|||||||||||||||||||
| Referral: |
Serum: 2.0 mL
Shipping & Storage: Store and ship refrigerated or frozen. Avoid repeated freeze-thaw cycles (#110-10-05 Serum / Plasma Separation Procedure & Transport)
|
|||||||||||||||||||
| Requisition: | ||||||||||||||||||||
| Reference Values: |
Plasma cortisol levels are normally highest around 8 am and lowest around 12 am.
Comment added to inpatient results: “Plasma cortisol can’t be interpreted in the context of exogenous steroids, estrogens, and critically ill patients. Clinical correlation is strongly urged.”
Method of Analysis: Competitive ECLIA Roche immunoassay
|
|||||||||||||||||||
| Availability: |
Daily
|
|||||||||||||||||||
| See Also: | ||||||||||||||||||||
| More Information: |
Interpretation & Assay Interferences: Multivitamins (45–125 µg biotin) or biotin-only supplements up to 1 mg per day do not interfere with cortisol assay. Samples should not be taken from patients receiving therapy with high biotin doses (i.e. >5 mg/day) until at least 8 hours after the last dose.
Oral contraceptives, pregnancy, or estrogen therapy cause elevated plasma cortisol levels due to an increase in binding proteins. Prednisolone, 6-α-methylprednisolone, or prednisone treatment may cause falsely elevated cortisol results. During metyrapone tests, 11-deoxycortisol levels are elevated. Falsely elevated cortisol values may be determined due to cross reactivity of the assay with 11-deoxycortisol. Patients suffering from 21-hydroxylase deficiency exhibit elevated 21-deoxycortisol levels and this can cause falsely elevated cortisol results. |