Screening — There are no broadly validated brief screening tests for cocaine abuse. Best studied are two tests modified from those used to screen for alcoholism: the 4-question CAGE and 2-question TICS. Both tests have sensitivities and specificities of 80 percent or greater in primary care settings for populations including women, pregnant women, the elderly, and patients with HIV infection.
Drug testing — Drug testing detects cocaine use, but is not diagnostic of cocaine abuse, which implies adverse consequences from use. Conversely, a negative drug screen may only indicate lack of recent use. Cocaine and its metabolites can be measured in urine, blood, oral fluid, sweat, and hair. The window of detection is shorter for cocaine than for its major metabolite, benzoylecgonine, and varies with the sensitivity of the assay method.
Urine testing (which measures benzoylecgonine, not cocaine) is common in clinical settings because the sample can be collected non-invasively. It has a detection window of about two to three days after cocaine use, but may be positive up to two weeks after chronic heavy use.
Blood testing has a detection window of 12 hours for cocaine and 48 hours for benzoylecgonine. It is rarely used outside the setting of acute intoxication. Actual blood cocaine concentrations have little correlation with acute symptoms of cocaine intoxication in the emergency department setting.
Oral fluid testing has a detection window similar to that of blood, with the advantage of non-invasive collection and better patient acceptability. Sweat testing (via patches worn on the skin) has a detection window of several weeks, but is useful only for prospective evaluation (ie, monitoring future drug intake). Results may be influenced by location of the skin patch and environmental exposure to cocaine.
Hair testing has the longest detection window (potentially years), but valid results require careful technique, and some questions remain unresolved. Results may be influenced by hair location, racial/ethnic differences in hair composition, prior hair treatments, and environmental exposure to cocaine. Cocaine continues to be incorporated into hair for a few months after last use.
A variety of relatively inexpensive commercial assays are available for testing of urine and oral fluid, including disposable kits that allow on-site testing with results available within minutes. Results from such screening tests should be confirmed by a standard laboratory assay, especially in legal or workplace settings.
Definitions and diagnosis — Cocaine abuse and dependence (sometimes termed addiction) are formal psychiatric diagnoses with explicit diagnostic criteria. These criteria, which apply to all psychoactive substances, are provided in the DSM-IV used in the US and the International Classification of Diseases-10th revision (ICD-10) used elsewhere in the world. The core diagnostic concepts, as well as the actual criteria, are very similar :
- Cocaine abuse is a “maladaptive pattern” of use that results in “clinically significant impairment or distress”.
- Cocaine dependence is loss of control over use, as reflected in continued use despite adverse effects and more use than originally intended.
Physical or pharmacological dependence (ie, tolerance or withdrawal) are not necessary for a diagnosis of psychological dependence. However, when present in a cocaine user, physical dependence is a powerful predictor of psychological dependence.
The diagnosis of cocaine abuse or dependence is made on the basis of history, obtained primarily from the patient, but also, when available, from collateral sources (eg, family, friends, and medical records). Several validated psychiatric questionnaires and structured interviews (such as the SCID [Structured Clinical Interview for DSM-IV] and the DIS [Diagnostic Interview Schedule]) are available to diagnose cocaine abuse or dependence but require time and trained staff. Therefore, they are generally used only in specialized treatment or research settings.
David A Gorelick, MD, PhD
H Nancy Sokol, MD