Abstract
Blood, oral fluid (saliva), urine and hair are the most commonly used biological matrices for drug testing in epidemiological drug research. Other biological matrices may also be used for selected purposes. Blood reflects recent drug intake and may be used to assess impairment. Oral fluid reflects drug presence in blood and thereby also recent intake, but drug concentrations in this matrix cannot be used to accurately estimate concentrations in blood. Urine reflects drug use during the last few days and in some cases for a longer period, but does not indicate the dose size or frequency of use. Hair reflects drug use during several months, but is a poor matrix for detecting use of cannabis. If using a single drug dose, this can be detected in blood and urine if the sample is taken within the detection timeframes, in most cases also in oral fluid. Single drug use is most often insufficient for producing a positive test result in a sample of hair. For cocaine and amphetamine, weekly use may be needed, while for cannabis a positive result is not guaranteed even after daily use. Refusal rates are lowest for oral fluid and highest for blood and hair samples. The analytical costs are lowest for urine and highest for hair. Combined use of questionnaires/interviews and drug testing detects more drug use than when using only one of those methods and is therefore expected to give more accurate data.
Highlights
Epidemiological studies of alcohol and drug use are most often performed by collecting self-reported data
In recent years an increasing amount of designer drugs have appeared on the market and these pose a problem for immunoassay screening as they often do not give a response on traditional immunoassays for e.g. amphetamines or cannabis
Dilution or PPT might be performed for expectorated oral fluid, while more extensive sample preparation is necessary for oral fluid collected with commercial sampling kits which contains preservatives, surfactants and in some cases dyes which might interfere with instrumental analysis
Summary
Epidemiological studies of alcohol and drug use are most often performed by collecting self-reported data. The detection timeframe for a drug is the average length of time after single use the drug can be detected in a biological matrix This depends on the elimination rate for the drug combined with the analytical cutoff concentration (the drug concentration above which a finding is regarded as positive). Some approximate detection times for individual drugs in blood, urine and oral fluid after single use have been published [19]. For non-specific methods, like immunological assays, false positive results are commonly observed and may be obtained because of the presence of other compounds than the one being analysed This may be a psychoactive substance, an inactive metabolite or a completely unrelated substance. The drug concentration in blood may indicate whether a therapeutic or supra-therapeutic dose has been taken
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