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A new ultraperformance-tandem mass spectrometry oral fluid assay for 29 illicit drugs and medications.
Clin Chem. 2009 Dec;55(12):2079-81
Authors: Huestis MA
Oral fluid testing also has disadvantages (6), as for any biological matrix. The volume of oral fluid is limited and may be reduced by drug consumption. Drug concentrations in oral fluid also are lower than in urine (e.g., benzodiazepines and cannabinoids), and their measurement therefore requires highly sensitive assays. Inhalation, smoking, oral, or insufflation administration may contaminate the oral mucosa, increasing concentrations and disrupting correlations with blood results. Another disadvantage is that excretion and concentrations vary with the pH of oral fluid given that the pH increases with the stimulation of oral fluid flow. Yet another limitation is the variation in the amounts of oral fluid collected within and between collection devices, which makes measurement of drug concentrations difficult. Such devices include buffers and surfactants to reduce drug adsorption to the container and collection pad that help improve drug recovery, but these additives dilute drug concentrations and can produce matrix interferences if oral fluid or diluted sample is injected directly into LC-MS instruments. Many investigators initially attempted direct injection or simple dilution procedures, but matrix effects frequently affected drug quantification. This consideration is important because additional preparation of oral fluid samples is usually necessary, increasing assay turnaround times, costs, and labor.
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"The current consensus in the field is that the wide variation in oral fluid/blood ratios in drivers thought to be under the influence of drugs does not allow reliable calculation of blood concentrations from the concentrations in oral fluid."
PMID: 19833833 [PubMed - indexed for MEDLINE]
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