Most Roadside THC Saliva Tests Vary Wildly in Accuracy
Of four oral fluid THC testing devices used in nearly 9,000 roadside tests, only one consistently detected THC with high accuracy, while two had sensitivity below 13%.
Quick Facts
What This Study Found
The Drager DrugTest had 96.8% sensitivity and 97.1% specificity for detecting THC at a 5 ng/mL threshold. In contrast, the AquilaScan and Druglizer devices had sensitivity below 13%, meaning they missed the vast majority of positive samples.
Key Numbers
Drager DrugTest: 96.8% sensitivity, 97.1% specificity, 97.0% efficiency. WipeAlyser Reader: 91.4% sensitivity, 97.2% specificity. AquilaScan and Druglizer: less than 13% sensitivity. Of 8,945 tests, 530 (5.9%) screened positive for THC.
How They Did This
Researchers conducted 8,945 oral fluid THC screening tests at the roadside using four different devices. Samples that screened positive (530 total, 5.9%) were confirmed by liquid chromatography-tandem mass spectrometry at multiple cutoff concentrations.
Why This Research Matters
As cannabis-impaired driving enforcement grows, police departments are adopting oral fluid testing devices. This study reveals that device choice matters enormously, with some devices essentially useless for detecting THC.
The Bigger Picture
Reliable roadside testing is essential for fair enforcement of impaired driving laws. When devices miss most positive cases, impaired drivers go undetected. When they produce false positives, sober drivers face unwarranted consequences.
What This Study Doesn't Tell Us
Field conditions (temperature, humidity) may have affected device performance. The study was conducted in one country (Brazil), and device performance may differ in other settings. Only THC was evaluated.
Questions This Raises
- ?Why do some devices perform so poorly in real-world conditions despite presumably passing laboratory testing?
- ?Should there be minimum performance standards for roadside oral fluid testing devices?
Trust & Context
- Key Stat:
- Sensitivity ranged from less than 13% to 96.8% across devices
- Evidence Grade:
- Large real-world sample with gold-standard LC-MS/MS confirmation, though conducted at a single location.
- Study Age:
- 2024 study
- Original Title:
- Reliability of roadside oral fluid testing devices for ∆9-tetrahydrocannabinol (∆9-THC) detection.
- Published In:
- Drug testing and analysis, 16(12), 1528-1536 (2024)
- Authors:
- Scherer, Juliana Nichterwitz, Vasconcelos, Mailton, Dalanhol, Carolina Silveira, Govoni, Bruna, Dos Santos, Bruno Pereira, Borges, Gabriela Ramos, de Gouveia, Giovanna Cristiano, Viola, Patrícia Pacheco, Carlson, Renato Luiz Romera, Martins, Aline Franco, Costa, Jose Luiz, Huestis, Marilyn A, Pechansky, Flavio
- Database ID:
- RTHC-05687
Evidence Hierarchy
A snapshot of a population at one point in time.
What do these levels mean? →Frequently Asked Questions
Which roadside THC saliva test performed best?
The Drager DrugTest had the best performance with 96.8% sensitivity and 97.1% specificity at a 5 ng/mL confirmation cutoff.
How reliable are roadside THC tests in general?
It depends entirely on the device. In this study, two devices missed nearly every positive sample (less than 13% sensitivity), while two others performed well (above 91% sensitivity).
Read More on RethinkTHC
Cite This Study
https://rethinkthc.com/research/RTHC-05687APA
Scherer, Juliana Nichterwitz; Vasconcelos, Mailton; Dalanhol, Carolina Silveira; Govoni, Bruna; Dos Santos, Bruno Pereira; Borges, Gabriela Ramos; de Gouveia, Giovanna Cristiano; Viola, Patrícia Pacheco; Carlson, Renato Luiz Romera; Martins, Aline Franco; Costa, Jose Luiz; Huestis, Marilyn A; Pechansky, Flavio. (2024). Reliability of roadside oral fluid testing devices for ∆9-tetrahydrocannabinol (∆9-THC) detection.. Drug testing and analysis, 16(12), 1528-1536. https://doi.org/10.1002/dta.3669
MLA
Scherer, Juliana Nichterwitz, et al. "Reliability of roadside oral fluid testing devices for ∆9-tetrahydrocannabinol (∆9-THC) detection.." Drug testing and analysis, 2024. https://doi.org/10.1002/dta.3669
RethinkTHC
RethinkTHC Research Database. "Reliability of roadside oral fluid testing devices for ∆9-te..." RTHC-05687. Retrieved from https://rethinkthc.com/research/scherer-2024-reliability-of-roadside-oral
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.