Adrenocorticotropic hormone (intact), Plasma

Diagnostic Use

ACTH in conjunction with cortisol is used to diagnose adrenal gland problems and pituitary diseases such as Cushing's disease/syndrome, Addison's, adrenal and pituitary tumours. ACTH is usually done as a diagnostic test once an abnormal cortisol level is detected.

Department

Endocrinology Lab

Delphic Registration Code

ACTH

Laboratory Handling

Phlebotomy

1 x EDTA. Collect on ice and send to lab immediately. Sample for ACTH must be sent in a tube for ACTH analysis only (no shared samples). Patient should be relaxed. Time of collect must be stated.

Synonyms

ACTH
Corticotrophin

Turnaround Time

7 days

Test Code

5428

Specimen Type

• Plasma

Specimen Requirements

Tube/Container Type:

Preferred

• EDTA (Lavender Cap)

Preferred Sample Volume (ml)

3

No of Samples Required

1

Paediatric Specimen Requirements

Tube/Container Type:

Preferred

• EDTA (Lavender Cap)

Preferred Sample Volume (ml)

1

Additional Specimen Information

Pre-Testing Requirements - Patient - need not be fasting but should be unstressed. A difficult venepuncture may cause increased ACTH secretion. Time of sampling must be stated (because of the diurnal variation in ACTH values) and the time of last dose of glucocorticoid (where relevant). In patients with Cushing's Syndrome it may be useful to take samples at 0900 hr and 2400 hr. Insulin hypoglycaemia or metyrapone testing are necessary when assessing hypothalamic - pituitary function.

Specimen Collection Protocols - Take 3 mL of EDTA anti-coagulated blood (purple top tube) and chill immediately in an ice/water mixture for 10 - 30 minutes, then centrifuge cold. Freeze plasma immediately. Even slight haemolysis must be avoided.
A sample for ACTH must be sent in a tube for ACTH analysis only (no shared samples).

Aliquot Instructions

Sample Type

• Plasma

Minimum Volume (ml)

0.5

Transport to Lab

Frozen
If overnight - Frozen

Additional Referral/Aliquot Information

>0.5 mL Plasma. No haemolysis. Freeze separated plasma for ACTH.
A sample for ACTH must be sent in a tube for ACTH analysis only (no shared samples).

Interpretation

Low ACTH results will be given by even slightly hemolysed samples.

Raised values – stress, Cushing’s Syndrome, (hypothalamic-pituitary disease or ectopic ACTH secretion from a tumour), ACTH secreting pituitary tumours with hyper pigmentation, (Nelson’s Syndrome), Addison’s Disease, Adrenal enzyme deficiency, adrenalectomy.

Undetectable values – Cushing’s Syndrome (adrenal adenoma or carcinoma) glucocorticoid therapy. Note that ACTH values may be undetectable in normal individuals, particularly in the late evening.

Reference Intervals

1.0 – 12 pmol/L (7 – 10am)

Test Method

Roche Cobas e411

Non-Funded Test Cost

$58.71 (Exclusive of GST)

Billing Code

5428

A sample for ACTH must be sent in a tube for ACTH analysis only (no shared samples). ACTH is very sensitive to hemolysis, but the rate of loss is reduced by chilling (but not freezing) blood, and by freezing plasma. Hemolysis as slight as 0.2 g/L Hb can cause significant loss of ACTH (Livesey and Dolamore, Clinical Biochemistry 43:1478-80 (2010)).

ACTH is rapidly destroyed by plasma enzymes - serum, heparin and fluoride samples are not acceptable as results are lowered. Warm thawed samples may not be assayed. Thawing and re-freezing the sample may elevate the levels.

Conversion factor: pg/ml = 4.5 x pmol/L

Contact Information

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