Oral Fluid Drug Testing: What Interferes With These On-Site Kits?

Abstract

On-site oral fluid (OF) based drug tests provide an immediate and non-invasive alternative to urine or blood screenings. Test kits use a lateral flow, competitive binding assay, providing semi-quantitative results within minutes. Kits can test for the presence of Methamphetamine, Amphetamine, Opiates, Cocaine, and Tetrahydrocannabinol (THC). These test kits could be used in a laboratory, or be self administered in the workplace, or used for roadside testing for law enforcement. Before integrating saliva drug tests in these environments, it’s important to determine ways of purposefully or unintentionally tampering with the tests that could result in false positive or false negative results. 
We collected 39 samples from male and female volunteers over 18 years old, with informed consent. Participants collected their saliva using a sponge swab. We tested effects of extreme temperatures before or after the sample was collected, alcohol, foods, or common medications. Confirmatory tests were performed using Liquid Chromatography/Mass Spectrometry. 
Results confirmed that kits can withstand hot and cold temperatures. However, a number of false positives and false negatives for THC were recorded. False negative results were noted for THC with the test kit compared to mass spectrometry. False positives with the test kit were linked to certain beverages when the beverages were used as saliva specimens. Mass spectrometry accurately verified THC presence/absence, highlighting the need for confirmatory drug testing. Further research examining the false positive/false negative results linked would provide valuable information to ensure that the on-site results are as reliable as possible.