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Test Code LAB61 Cortisol, Blood

Performing Laboratory

St. Louis Children's Hospital Laboratory - Chemistry

Specimen Requirements

Patient Preparation: Samples should not be taken from patients receiving therapy with high biotin doses (i.e., >5 mg/day) until at least 8 hours following the last biotin administration

Collection Container/Tube:

Preferred: Mint green-top lithium heparin (MNTGRN LiHep) tube

Acceptable: Green samplette/microtainer, plain red-top tube, Gold SST gel tube, or Lavender-top (EDTA) tube

Submission Container/Tube: If specimen is coming from outside facility and collected in a microtainer, plain red-top tube or lavender-top tube, aliquot processed sample into a plastic vial for transport (labeling with specimen type)

Specimen Collection Volume: 1.0 mL (minimum 0.6 mL)

Special Instructions: Send to lab promptly

 

Sample Rejection

Mislabled or unlabeled specimens

Logistics

Test Availability: Monday-Sunday

Cut-off time: None, performed as received

Turnaround Time: Same Day; 2 hours from receipt in performing lab

Reference Values

Reference Interval: (all ages)

AM: 4.8-19.5 mcg/dL
PM: appoximately half of morning value
NOTE: Circulating cortisol undergoes marked diurnal variations. Time of sample collection must be considered when interpreting results. Cortisol reference intervals are not well established in pediatric populations.

Critical Value: None established

 

Methodology

Electrochemiluminescence immunoassay (ECLIA) - competition principle

Limitations

  • In rare cases, interference due to extremely high titers of antibodies to analyte-specific antibodies, streptavidin or ruthenium can occur.
  • In samples from patients who have been treated with prednisolone, methylprednisolone or prednisone, falsely elevated concentrations of cortisol may be determined.
  • During metyrapon tests, 11-deoxycortisol levels are elevated. Falsely elevated cortisol values may be determined due to cross reactions.
  • Samples should not be taken from patients receiving therapy with high biotin doses until at least 8 hours following the last biotin administration.

Reference: Package Insert Roche Cobas Cortisol Version; 2008-04, V2 English

Additional Information

FOR SLCH CORE LABORATORY USE ONLY

Lab Processing Instructions: Centrifuge to separate. If specimen is collected in a microtainer, plain red-top tube or lavender-top tube aliquot sample into a Roche false-bottom tube for testing (labeling aliquot with specimen type).

Processed Volume: minimum 0.3 mL plasma/serum

Analyte Stability:

Specimen Type Temperature Time
Whole Blood (unprocessed)  Ambient 24 hours
Plasma/Serum (processed) Refrigerated (preferred) 5 days
  Ambient  24 hours    
  Frozen  3 months      
Specimens should only go through one Freeze /thaw cycle

Test Classification and CPT Code

82533

LOINC

2143-6

Last Reviewed

06/2025