Systematic review finds roadside cannabis screening tests need improvement
A systematic review of roadside cannabis screening tests found that existing oral fluid devices can detect recent cannabis use but struggle to reliably indicate actual impairment, creating challenges for enforcement.
Quick Facts
What This Study Found
Available roadside screening devices, primarily oral fluid-based, can detect THC presence but their ability to identify functional impairment is limited. Sensitivity and specificity varied across devices and cutoff thresholds.
Key Numbers
Multiple roadside screening devices evaluated. Oral fluid testing was the primary modality. Sensitivity and specificity varied by device and THC cutoff threshold.
How They Did This
Systematic review of six databases (inception to March 2020) and grey literature. Included primary studies evaluating test characteristics of roadside cannabis screening compared to laboratory confirmation testing.
Why This Research Matters
As cannabis legalization expands, effective roadside screening is essential for traffic safety. Unlike alcohol, where breathalyzers directly measure impairment-related blood alcohol levels, cannabis detection does not straightforwardly indicate impairment.
The Bigger Picture
The cannabis impairment detection gap is one of the most significant practical challenges of legalization. THC can remain detectable long after impairment has resolved, while some impaired drivers may test below detection thresholds depending on timing.
What This Study Doesn't Tell Us
Literature search through March 2020 may miss newer devices. Varied study designs and reference standards across included studies. Roadside conditions differ from laboratory settings. Cannot validate impairment detection, only THC presence detection.
Questions This Raises
- ?Would combining oral fluid THC testing with cognitive/behavioral assessment improve impairment identification?
- ?What THC thresholds best balance sensitivity and specificity for enforcement purposes?
Trust & Context
- Key Stat:
- Oral fluid devices detect THC but cannot reliably indicate impairment
- Evidence Grade:
- Systematic review with appropriate methodology. Limited by heterogeneous study designs and the fundamental challenge of measuring cannabis impairment.
- Study Age:
- Published 2023. Literature through March 2020.
- Original Title:
- Roadside screening tests for cannabis use: A systematic review.
- Published In:
- Heliyon, 9(4), e14630 (2023)
- Authors:
- Wennberg, Erica, Windle, Sarah B(4), Filion, Kristian B(4), Thombs, Brett D, Gore, Genevieve, Benedetti, Andrea, Grad, Roland, Ells, Carolyn, Eisenberg, Mark J
- Database ID:
- RTHC-05022
Evidence Hierarchy
Analyzes all available research on a topic using a structured method.
What do these levels mean? →Frequently Asked Questions
Can police test for cannabis at the roadside?
Yes, oral fluid (saliva) testing devices can detect recent cannabis use at the roadside. However, this review found these tests have significant limitations. They detect THC presence, not impairment, and their accuracy varies by device and cutoff threshold.
Why is testing for cannabis impairment so difficult?
Unlike alcohol, where blood alcohol concentration directly correlates with impairment, THC levels do not reliably predict how impaired someone is. Frequent users may have high THC levels even when not impaired, while occasional users may be significantly impaired at lower levels. This makes setting meaningful legal thresholds extremely challenging.
Read More on RethinkTHC
Cite This Study
https://rethinkthc.com/research/RTHC-05022APA
Wennberg, Erica; Windle, Sarah B; Filion, Kristian B; Thombs, Brett D; Gore, Genevieve; Benedetti, Andrea; Grad, Roland; Ells, Carolyn; Eisenberg, Mark J. (2023). Roadside screening tests for cannabis use: A systematic review.. Heliyon, 9(4), e14630. https://doi.org/10.1016/j.heliyon.2023.e14630
MLA
Wennberg, Erica, et al. "Roadside screening tests for cannabis use: A systematic review.." Heliyon, 2023. https://doi.org/10.1016/j.heliyon.2023.e14630
RethinkTHC
RethinkTHC Research Database. "Roadside screening tests for cannabis use: A systematic revi..." RTHC-05022. Retrieved from https://rethinkthc.com/research/wennberg-2023-roadside-screening-tests-for
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.