Specimen Collection
Casual urine
Reference Intervals
The screen is reported as
detected
or
not detected
or
trace
depending on the cannabis level:
|
Not detected
|
<25 ng/mL
|
|
Trace
|
25-50 ng/mL
|
|
Detected
|
>50 ng/mL
|
This test does NOT detect synthetic cannabinoids
Uncertainty of Measurement
: 10% at the level of 50 ng/mL.
Turnaround Time: Within 1 day
Availability
:
Drug screens can be performed after hours and on weekends for urgent samples (AED/CED), or if approved by the on-call Chemical Pathologist.
The request form must be clearly marked '
Urgent'
and the laboratory must be alerted by telephone (via Lablink) before the sample is sent.
Assay Method
Principle
: Immunoassay
Diagnostic Use and Interpretation
Frequent users:
Cannabis and its metabolites are stored in body fat and so are eliminated slowly from the body. They may continue to be detected in the urine after long periods of abstinence. Infrequent users will eliminate the cannabis more rapidly because less is stored in body fat. For example, smoking a single "joint" may result in cannabis being detectable in the urine for up to 36 hours, whereas a frequent user may have detectable cannabis up to 10 weeks after cessation of cannabis smoking.
The urine
cannabinoid / creatinine ratio
(ug cannabinoid / mmol creatinine) is useful for serial monitoring. This ratio fluctuates less from day to day than the concentrations expressed as ng/mL. An increase in the ratio of > 50% between two samples taken at least 48 hours apart indicates cannabis has been used in the intervening period.
Medico-legal limits for the cannabinoid/creatinine ratio have not been defined, and its use must therefore be confined to non-evidential or clinical purposes.
It is extremely unlikely that a passive smoker could have urine concentrations > 20 ng/mL.
Drugs detected:
This test detects only THC (tetrahydrocannabinol) and THC metabolites. It does
not
detect synthetic cannabinoids.
Drug Screen- Clinical management
Drug Screen- Evidential purposes
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