Specimen Collection
SPECIMEN:
Only samples collected at
bedtime
have any diagnostic value.
Specimens taken at other times
will not be processed
, except by special arrangement with the Chemical Pathologist.
Saliva is collected at the patient's usual bedtime, before brushing teeth or flossing.
-
Two acceptable methods of collection are: using a Salivette (obtainable from the laboratory). The cotton wool swab is removed from the salivette and placed in the mouth until saturated (1 to 3 min), then replaced in the salivette, and capped.
-
Direct spitting into a wide-mouthed container. At least
2 mL
of saliva is required.
NOTE:
The
time
and
date
of collection must be noted on the request form.
After collection, the specimen can be kept at room temperature (for up to 24 hours), refrigerated (for up to 72 hours), or frozen if the time before delivery to the laboratory is likely to be longer than 72 hours.
Note:
(a) Any mixture of blood in the specimen, (e.g. from a lesion in the mouth, such as caused by flossing) will invalidate the result.
(b) The test is only valid if the patient has an established normal sleep cycle (e.g. it may be invalid in patients who have recently worked on night shift).
(c) The test may be invalid if the patient is on any form of glucocorticoid therapy (e.g. asthma inhaler).
This test may be vetted by a pathologist.
The clinical information for the test must be clearly written on the request form. If clinical information is not provided, or does not provide sufficient justification for the test, the test may be declined.
Declined tests
:
If a test is declined, the specimen will be held for a reasonable period (usually 3 weeks but dependant on the stability of the sample). Medical practitioners seeking approval for a declined test should email the on-call Chemical Pathologist (
chemicalpathologist@adhb.govt.nz
) , giving the patient's name and NHI number and the clinical justification for the test. If unable to email, call the on-call Chemical Pathologist via Lablink (09-3078995) and identify yourself as a doctor.
Test vetting policy
Reference Intervals
Units:
nmol/L
|
Reference interval:
less than 6 nmol/L
|
Uncertainty of Measurement:
15%
Limit of detection
: 3 nmol/L.
Turnaround Time: Within 1 week
Assay Method
Principle
: Competitive immunoassay with electrochemiluminescence detection
Assay
: Roche cortisol II
Analyser
: Cobas e802
Diagnostic Use and Interpretation
Screening for Cushings syndrome is the only established indication for this test.
Other screening tests for Cushing's syndrome are:
- 24h urine cortisol
- bedtime spot urine cortisol / creatinine ratio
- overnight low-dose dexamethasone test
References:
1. Papanicolau DA, Mullen N, Kyrou I. Night-time salivary cortisol: a useful test for the diagnosis of Cushing's syndrome. J Clin Endocrinol Metab 2002; 87: 4515-4521.
2. Raff H, Raff JL, Findling JW. Late-night salivary cortisol as a screening test for Cushing's syndrome. J Clin Endocrinol Metab 1998:83;2681-2686.
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.
After-hours
: contact
Lablink (Auckland City Hospital ext. 22000 or 09-3078995) or hospital operator for on duty staff after hours.
Dr Samarina Musaad
(Clinical Lead)
:
SamarinaM@adhb.govt.nz
ext. 22402
Dr Cam Kyle:
CampbellK@adhb.govt.nz
ext 22052
Dr Weldon Chiu:
WeldonC@adhb.govt.nz
ext. 23427
Dr Campbell Heron:
CHeron@adhb.govt.nz
ext. 23427
Dr Sakunthala Jayasinghe:
Sakunthala@adhb.govt.nz
ext. 23427
Specimen Transport Instructions for Referring Laboratories
The time of collection must be noted on the request form (should be between 9pm - midnight).
Transport times to the laboratory:
Room temperature - if within 24 hours of collection
Refrigerated - up to 72 hours
Frozen - if time to the laboratory is greater than 72 hours