Oral fluid for workplace drug testing: laboratory implementation

As oral fluid increases in popularity for workplace testing, due to its easy and observed collection, the ability to adapt existing laboratory instrumentation without further capital investment will allow more facilities to test oral fluid. The European Workplace Drug Testing Society (EWDTS) guidelines for oral fluid testing outline the maximum cut-off concentrations acceptable under the workplace drug testing programme. The recommended cut-off values may be subject to change as advances in technology or other considerations warrant identification of these substances at different concentrations; however, the instrumentation currently exists for routine screening using immunoassay and confirmation by gas chromatography-mass spectrometry (GC-MS) or liquid chromatography with tandem mass spectral detection (LC-MS/MS) so laboratories can easily implement oral fluid analysis in their current systems. Immunoassays for the detection of the drug classes at recommended levels have been developed using various collection devices and different formats: liquid reagent chemistries and enzyme-linked immunosorbent assay (ELISA) platforms. Immunoassays provide faster turnaround than mass spectral methods particularly when the number of specimens increases. Since the guidelines state that positive immunoassay results should not be reported without confirmation, fully validated methods using LC-MS/MS and/or GC-MS for all drugs are also widely available. All proposed concentrations are easily achievable using MS instruments currently in testing laboratories; however, the likelihood of a low number of positive specimens in workplace populations allows the test facility to screen specimens in a cost-effective manner using immunoassay, while ensuring scientific credibility and defensibility by confirming the positive results with a second test.