Correct diagnosis of marijuana use is a key first step in dealing with an individual's drug problems. Traditionally, the most objective criterion available for identifying marijuana use is urine testing. Urinalysis is the most widely used technique and provides an objective measure for determining whether recent drug use has occurred over the past 2 to 4 days. Recently, interest has gown in improving urinalysis techniques and adopting other biological fluids and tissues, such as saliva, sweat, and hair, that may reveal additional information about an individual's drug use patterns.

Saliva testing, in comparison to urinalysis, offers different information regarding recency of marijuana use. The detection times for tetrahydrocannabinol, the active ingredient in marijuana, in saliva is similar to that for blood (4 to 12 hours).

Consequently, saliva testing offers the possibility of revealing current drug use that affects an individual's performance in complex psychomotor tasks such as driving and operating heavy equipment.

Sweat testing has recently become feasible through the development of a new sweat patch device designed to collect nonvolatile drugs of abuse from human skin. The device is applied like a bandage to the skin. Substances with the volatility of water or greater leave the device through a membrane barrier. Nonvolatile substances are concentrated on an absorption pad inside the patch. Subjects can wear the-patch for up to several weeks. The patch is then removed and stored, and the contents analyzed. Preliminary studies with the sweat patch indicate that it may be useful for the detection-of drug use over a period of I to 2 weeks- Currently, its usefulness-is being evaluated.