NCJ Number
162175
Date Published
Unknown
Length
12 pages
Annotation
This chapter describes laboratory tests to detect the presence of cannabinoids and reasons for choosing one test rather than another.
Abstract
A number of laboratory tests detect the presence of cannabinoids. The choice of test depends primarily on whether it is to serve as a screening tool, to confirm a diagnosis of marijuana abuse in an individual patient, or to monitor the results of a patient's treatment program. The fundamental trade-off among the various techniques is low cost/ease-of-use versus accuracy. Unlike blood-alcohol tests, marijuana urine-testing cannot reliably be correlated with concurrent behavioral effects. Urinalysis establishes only that marijuana use occurred within the several weeks preceding specimen collection. Salivary tests can narrow the time frame to about twelve hours, but both these tests provide evidence of marijuana use, not of intoxication or impairment, which must be established by a formal mental-status examination and a careful history. Laboratory testing methods include: (1) thin-layer chromatography (inexpensive but not as sensitive as other tests); (2) immunoassay (rapid, low-cost, but major drawback is cross-reactivity resulting in false-positive results); and (3) gas chromatography/mass spectrometry (highly accurate but expensive). Table, references