Laboratory Test Information Guide

Details for Cortisol, Plasma/Serum

Test Name: Cortisol, Plasma/Serum
Alternate Name(s):  
Laboratory: Core
Specimen Type: Adult:
4.5 mL Light Green top (Li-Heparin) Vacutainer tube

0-2 years: 0.5 mL Light Green top (Li-Heparin) Microtainer
2-10 years: 3 mL Light Green top (Li-Heparin) Vacutainer tube

Red, Gold, or Lavender (EDTA) top tubes are also acceptable
Collection Information: Minimum volume of plasma or serum required is 700 L for adult samples or 200 L for pediatric samples.
Test Schedule: As required
Turnaround time from when specimen
is received in testing laboratory:
4 hours
Reference Range: 6 10 am: 133 537 nmol/L

4 8 pm: 68 327 nmol/L
Effective Date: 2018-03-06
Revised Date: 2018-08-17
Critical Value:  
Interpretive Comments: Plasma cortisol levels are normally highest around 8 am and lowest around 12 am.
Special Processing:  
Comments: Biotin may interfere with this test. Samples should not be taken from patients receiving high biotin doses (i.e. > 5 mg/day) until at least 8 hours after the last biotin administration.

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 metyrapon 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.
Method of Analysis: Roche Electrochemiluminescence
Critical Information Required:  
Storage & Shipment:  
System Codes: 
Referred To:  

Questions? Comments? Contact Laura Gopaul