Specimen Collection
PROCEDURE:
The test can be performed at any time of the day.
Please refer ADHB Outpatient requests to the Endocrinology Clinic at Greenlane Clinical Centre.
Requests from GPs for this test should be directed to the Endocrinology Outpatient Service at Greenlane Clinical Centre for booking (see Endocrine Nurse numbers)
.
The Synacthen is obtained from Pharmacy, not the laboratory. Synacthen is a synthetic form of ACTH.
1. Insert a butterfly needle into the vein. Withdraw the pre-synacthen cortisol sample: 5 mL blood into a heparin PST tube. Request "
cortisol
" on the form, write the time, and send immediately to the laboratory. If ACTH is required also collect 5 mL blood into a chilled EDTA tube (on ice).
2. Infuse 250 ug synacthen over 1 minute. The butterfly needle can now be removed or flushed with saline and kept in.
3. After 30 minutes, withdraw the post-synacthen cortisol sample: 5 mL blood into a heparin PST tube. Use a
separate
form, request "
post-synacthen cortisol"
, write the time, and send in a separate bag. (If the butterfly has been kept in, first withdraw enough blood to wash out the saline before collecting the blood sample; dilution with saline will give a false low result).
Reference Intervals
Reference interval below applies to the 30-min test
|
time
|
plasma cortisol (nmol/L)
|
|
0
|
High values are common in sick or stressed patients.
Low values
< 170
in the morning suggest adrenal insufficiency.
|
|
30 min
|
>400
normal response (except in patients on OCP or estrogen therapy) .
A normal result can occur in partial or recent onset ACTH deficiency (e.g. recent pituitary surgery). If clinical concern exists,
discuss
with an endocrinologist .
< 400
Post-synacthen cortisol <400 suggests adrenal insufficiency (primary or secondary) or adrenal suppression from exogenous steroids. If the cause is not clear, consider further evaluation and referral to an endocrinologist
|
Notes
:
1.
If on estrogen therapy or an OCP, a post-synacthen cortisol below 600 nmol/L suggests adrenal insufficiency (primary or secondary).
2. The 30-minute test is recommended. The cutoff value for the 60-min test is about 15% higher (460 nmol/L).
3. Low-dose ACTH test: the normal cortisol response to 1 ug of ACTH is almost the same as for 250 ug ACTH
3. A new cortisol assay (Roche cortisol II) has been in used from 2 Sept 2015. Results are approx. 26% lower than with the old assay.
Turnaround Time: Within 3 hours
Diagnostic Use and Interpretation
Primary adrenal insufficiency:
Marked elevation of plasma ACTH, usually > 100 pmol/L.
Secondary adrenal insufficiency
(hypopituitarism or adrenal suppression by glucocorticoids):
Normal or low ACTH.
A normal synacthen test does not exclude secondary adrenal insufficiency, especially if ACTH deficiency is of recent onset . Additional endocrine tests may be necessary, such as the Insulin tolerance test or overnight Metyrapone test .
Contact Information
Emails to
chemicalpathologist@adhb.govt.nz
will receive priority attention from the on-call chemical pathologist.
If the query concerns a specific patient please include the NHI number in your email.
If email is not a suitable option, please contact the on-call chemical pathologist via
Lablink (Auckland City Hospital ext. 22000 or 09-3078995).
Individual chemical pathologists may be contacted but will not be available at all times.
Valerie Cheetham (Endocrine Nurse):
Ext. 26871
Christine McGrail (Endocrine Nurse):
Ext. 26854
Joan Callis (Endocrine Nurse):
Ext. 26855
Dr Cam Kyle (Clinical Head)
:
CampbellK@adhb.govt.nz
ext 22052 or mobile 027 276 0038
Dr James Davidson:
jamesd@adhb.govt.nz
ext 25985 or mobile 021 774 656
Dr Weldon Chiu:
WeldonC@adhb.govt.nz
ext 22045 or mobile 027 290 1073
Dr. Leo Lam (Registrar):
ChiSingL@adhb.govt.nz
ext 22045 or mobile 021-442-408