Cortisol - Serum or Plasma - Northern Region Test Guide

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Auckland Te Toka Tumai

Test Guide

Cortisol – Serum or Plasma

Testing Laboratory

Auckland Te Toka Tumai | Auckland Hospital

Department

Chemical Pathology

Delphic Registration Code (Alpha Code)

COR

Test Code (Numeric Code)

3006

Laboratory Handling

Phlebotomy

See notes below

Registration

Cortisol {Plain, Heparin, EDTA - Timed specimens require separate numbers.

Separating

Treat Rapid serum cortisol requests as orange forms and hand deliver at each step of the process . The yellow form must accompany the specimen throughout the process.

Test Adds Requirement

Rapid serum cortisol (Adrenal Catheter placement) - Lablink: Note requirements under Specimen Collection in regards to arranging this test request. Please refer calls related to these samples to the Automation Section Leader or a Technical Specialist so that the correct tracking form can be filled out.

Sample Stability

24 hours at 20-25°C, 4 days at 2-8°C, 12 months at -20°C

Synonyms

Cortisol

Turnaround Time

3 hours

Specimen Type

Plasma
Serum

Specimen Requirements

Tube/Container Type:

Preferred

Lithium Heparin PST- Gel (Light Green Cap)

Acceptable

EDTA (Lavender Cap)
Lithium Heparin - Non-gel (Green Cap)
Lithium Heparin PST- Gel (Light Green Cap)
Plain (Red Top)
SST II (Gold Cap)

Paediatric Specimen Requirements

Tube/Container Type:

Preferred

Heparin (Microtainer)

Acceptable

EDTA (Microtainer)
Plain(Microtainer)
EDTA (Lavender Cap)
Lithium Heparin - Non-gel (Green Cap)
Lithium Heparin PST- Gel (Light Green Cap)
Plain (Red Top)
SST II (Gold Cap)

Pre-testing Requirements

Specimen Collection

Rapid serum cortisol (Adrenal Catheter placement): These must be arranged with the Section Head of Automation, Chemical Pathology, LabPlus (ext 22118, or contact via LabLink ext 22000) at least one day before the catheter placement procedure. The turnaround time is approximately 35 minutes from receipt of the sample.

Hand deliver samples to ensure no transport delays.

Synacthen and dexamethasone tests:
Pre-synacthen or pre-dexamethasone samples: request " cortisol " . Send immediately.

Post-synacthen sample: Use separate form and request "post-synacthen cortisol" . Send in a separate bag

Post-dexamethasone sample: Use separate form and request "post-dexamethasone cortisol" . Send in a separate bag

Sample stability:

Additional Specimen Information

4.5 mL PST Blood (Preferred)
Micro-PST 0.5 mL Paediatric Micro-PST Blood (Preferred)
EDTA 4 mL EDTA Blood
Heparin 5 mL Heparin Blood
Plain 4 mL Plain Blood
SST 3.5 mL SST Blood
Microsample 0.5 mL Paediatric Microsample Blood

Diagnostic Use

Random or early morning cortisol measurements are of limited value due to the diurnal variation. Appropriate stimulation or suppression tests are usually necessary to determine the status of the HPA axis.

Hypercortisolism (Cushing’s syndrome) may be due to pituitary or adrenal tumours, or to ectopic ACTH-secreting tumours.

In Cushing’s syndrome, the early morning cortisol is often within the reference interval.

Screening tests for Cushings syndrome:

24 hour urine cortisol
Bedtime urine cortisol/creatinine ratio
Bedtime plasma cortisol
Bedtime salivary cortisol
Overnight low-dose dexamethasone suppression test
Plasma cortisol concentrations are decreased in Addison’s disease and hypopituitarism and in patients taking synthetic glucocorticoids (e.g. prednisone, dexamethasone).An ACTH level can help to distinguish these conditions. Past prolonged exogenous steroid use can suppress endogenous ACTH and steroid production for weeks to months, even after stopping the exogenous steroid. A careful examination of the patient’s medications, including oral, topical, inhaled, intra-articular and other injected steroids is important in this situation. Steroids injected into joints etc. may have a very long half-life (days to weeks). Some remedies/supplements bought overseas may have added steroids and may be associated with abnormal cortisol results. If the clinical features do not match the laboratory results, please contact the on-call chemical pathologist.

Interpretation

Variable cross-reactivity with other steroids can occur as demonstrated in the downloadable document below (see ” Roche Elecsys Cortisol II assay steroid cross-reactivity”).

Dexamethasone Test

Synacthen test

Download: Roche Elecsys – Cortisol II assay steroid cross-reactivity.docx

Reference Intervals

Morning sample reference interval (6 to 10 a.m.) : 170 – 500 nmol/L

There is a diurnal variation in plasma cortisol; the level is highest shortly before waking and lowest at bedtime.
The following comments apply to early morning samples if the patient is not undergoing an adrenal suppression or stimulation test:
1. An early morning serum cortisol < 170 nmol/L in the absence of recent exogenous steroids is suggestive of primary or secondary adrenal insufficiency. A synacthen stimulation test may be indicated.
2. Early morning cortisol between 170 and 300 nmol/L in the absence of recent exogenous steroids: adrenal insufficiency (primary or secondary) is unlikely but possible. If clinical concern exists, discuss with an endocrinologist .
3. A plasma cortisol higher than 300 nmol/L in an unstressed person excludes adrenal insufficiency (primary or secondary) in the vast majority of cases.
Notes: a new cortisol assay has been used from 2 Sept 2015. The results are approximately 26% lower than the old assay. New reference intervals apply.

Test Method

Principle : Competitive type immunoassay with chemiluminescence detection

Reagents: Roche Elecsys Cortisol II

Analyser: Cobas e801

Uncertainty of Measurement

Uncertainty of Measurement: 6%

Last updated: 26/03/2026

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A B C D E F G H I J K L M N O P Q R S T U V W X Y Z #

Cortisol – Serum or Plasma

Testing Laboratory

Department

Delphic Registration Code (Alpha Code)

Test Code (Numeric Code)

Laboratory Handling

Phlebotomy

Registration

Separating

Test Adds Requirement

Sample Stability

Synonyms

Turnaround Time

Specimen Type

Specimen Requirements

Tube/Container Type:

Preferred

Acceptable

Paediatric Specimen Requirements

Tube/Container Type:

Preferred

Acceptable

Pre-testing Requirements

Additional Specimen Information

Diagnostic Use

Interpretation

Reference Intervals

Test Method

Uncertainty of Measurement

Non-Funded Test Cost

Additional Costing Information

Contact Information

Enquiry Form

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Cortisol – Serum or Plasma

Overview

Testing Laboratory

Department

Delphic Registration Code (Alpha Code)

Test Code (Numeric Code)

Laboratory Handling

Phlebotomy

Registration

Separating

Test Adds Requirement

Sample Stability

Synonyms

Turnaround Time

Specimen

Specimen Type

Specimen Requirements

Tube/Container Type:

Preferred

Acceptable

Paediatric Specimen Requirements

Tube/Container Type:

Preferred

Acceptable

Pre-testing Requirements

Additional Specimen Information

Referral

Clinical Information/Test Method

Diagnostic Use

Interpretation

Reference Intervals

Test Method

Uncertainty of Measurement

Price

Non-Funded Test Cost

Additional Costing Information

Additional Information

Contact Information

Contact Information

Enquiry Form

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