Oral Fluid Testing

Abstract

Oral fluid is a specimen that has gained popularity over the past 20 years as an alternative matrix for drug testing. Although the terms oral fluid and saliva are often used interchangeably, they are physiologically different. Saliva is a fluid secreted from granules in the acini (small sacs lined with secretory cells) of the salivary glands. Oral fluid encompasses not just saliva but also gingival crevicular, nasal, and bronchial secretions and other components such as bacteria, cellular elements, electrolytes, immunoglobulins, proteins, and food debris. There are a number of factors that influence the transfer of drugs into the oral fluid, including oral fluid composition, flow rate, pH, the drug’s pKa, protein binding, lipophilicity, spatial configuration, and molecular size. Oral fluid testing has been used in drug abuse, pain management, and drugged driving testing. Oral fluid differs from urine drug testing in that parent drugs are often the targeted analytes. Several collection devices are commercially available to collect oral fluid. Screening of oral fluid for drugs can be performed simply by immunoassay either on-site or in the laboratory. A more broad-based screening or confirmation can be performed using mass spectrometry or by hyphenated chromatography-mass spectrometry techniques. When interpreting oral fluid test results, the following factors unique to oral fluid should be considered: appropriate cutoff concentrations of screen and confirmation tests; medical conditions affecting oral fluid flow or composition and drug transfer to oral fluid; analyte stability during storage; oral cavity contamination from smoked, unencapsulated oral, insufflated, vaporized, or inhaled administration of drugs; and the detection times of drugs in oral fluid.