Drugs of Abuse Testing

For most drugs of abuse testing, results of initial screening testing are compared with a predetermined cut-off. Anything below that cut-off is considered negative; anything above is considered a positive screening result.

Within each class of drug that is tested, there may be a variety of chemically similar drugs. Legal substances that are chemically similar to illegal ones can produce a positive screening result. Therefore, screening tests that are positive for one or more classes of drugs are frequently confirmed with a secondary test that identifies the exact substance present using a very sensitive and specific method, such as gas chromatography/mass spectrometry (GC/MS).

Some of the most commonly screened drug classes are listed in the table below.

For a more comprehensive list of drug classes and drugs of abuse, click here.

Substances that are not similar to the defined classes can produce false negative results. Some drugs may be difficult to detect with the standardized assays, either because the test is not set up to detect the drug, such as methylenedioxy-methamphetamine (MDMA, Ecstasy), oxycodone (Oxycontin), or buprenorphine, or because the drug does not remain in the body long enough to be detected, such as gamma-hydroxybutyrate (GHB).

For sports testing of hormones and steroids, each test performed is usually specific for a single substance and may be quantitative. Athletes, especially those at the national and international level, are tested for illegal drugs and are additionally governed by a long list of prohibited substances called performance enhancers.

Groups of drug tests are typically ordered for medical or legal reasons, as part of a "drug-free workplace" or as part of a sports testing program. People who use these substances ingest, inhale, smoke, or inject them into their bodies. The amounts that are absorbed and the effects that they have depend on the which drugs are taken, how they interact, their purity and strength, the quantity, timing, method of intake, and the individual person's ability to metabolize and excrete them. Some drugs can interfere with the action or metabolism of other medications, have additive effects such as taking two drugs that both depress the central nervous system (CNS), or have competing effects such as taking one drug that depresses the CNS and another that stimulates it. The drugs tested for are not normally found in the body, with the exception of some hormones and steroids measured as part of sports testing.

Urine and saliva are collected in clean containers. A blood sample is obtained by inserting a needle into a vein in the arm. Hair is cut close to the scalp to collect a sample. A sweat sample is typically collected by applying a patch to the skin for a specified period of time.