Oral fluid testing is done using the fluid within the oral cavity as the specimen for testing. When doing an oral fluid point-of-care test (POCT) it is usually screening for the presence of the parent drug and/or gross metabolites. When a lab test is done with oral fluid it is looking for the gross metabolites of cannabis. The image below shows a lab oral fluid test being done. A swab (on the end of a stick) is swirled around in the mouth to obtain the specimen and then placed in the tube (which is filled with a buffer fluid) and the tube is then sent into the lab for testing. Buffer fluid is used to stabilize the specimen for shipment and testing. 
Oral fluid tests are most often used when the tester is looking for information about what the donor has done in recent history. The tests do not show use from weeks ago, they are most effective for showing recent use. Oral fluid tests are also often chosen due to the ease of administration and because they are difficult to adulterate. This type of testing is becoming more and more widely used in Canada for these reasons, particularly with the legalization of cannabis and employers wanting to test only for recent use.
