A placebo-controlled study to assess Standardized Field Sobriety Tests performance during alcohol and cannabis intoxication in heavy cannabis users and accuracy of point of collection testing devices for detecting THC in oral fluid
Standardized Field Sobriety Tests (SFST) and oral fluid devices are used to screen for driving impairment and roadside drug detection, respectively. SFST have been validated for alcohol, but their sensitivity to impairment induced by other drugs is relatively unknown. The sensitivity and specificity for Δ(9)-tetrahydrocannabinol (THC) of most oral fluid devices have been low.
This study assessed the effects of smoking cannabis with and without alcohol on SFST performance. Presence of THC in oral fluid was examined with two devices (Dräger Drug Test® 5000 and Securetec Drugwipe® 5).
Twenty heavy cannabis users (15 males and 5 females; mean age, 24.3 years) participated in a double-blind, placebo-controlled study assessing percentage of impaired individuals on the SFST and the sensitivity of two oral fluid devices. Participants received alcohol doses or alcohol placebo in combination with 400 μg/kg body weight THC. We aimed to reach peak blood alcohol concentration values of 0.5 and 0.7 mg/mL.
Cannabis was significantly related to performance on the one-leg stand (p = 0.037). Alcohol in combination with cannabis was significantly related to impairment on horizontal gaze nystagmus (p = 0.029). The Dräger Drug Test® 5000 demonstrated a high sensitivity for THC, whereas the sensitivity of the Securetec Drugwipe® 5 was low.
SFST were mildly sensitive to impairment from cannabis in heavy users. Lack of sensitivity might be attributed to tolerance and time of testing. SFST were sensitive to both doses of alcohol. The Dräger Drug Test® 5000 appears to be a promising tool for detecting THC in oral fluid as far as correct THC detection is concerned.
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"During the evaluation of the previous DrugWipe5 version with confirmation of THC in serum, Bosker et al.  observed that the test's performance was optimum 15 min after smoking, and as time after smoking progressed, the percentages of false negatives increased and sensitivities were low. Toennes et al.  found a sensitivity and efficiency of approximately 90% when evaluating the DrugWipe 5 + with OF confirmation. "
"   While some individual components of the SFST, such as the one-leg-stand test,   have been documented to be fairly consistent predictors of cannabis-influenced behaviour, other SFST components , such as the walk-and-turn test and the horizontalgaze-nystagmus test, have not been shown to be reliable methods for identifying subjects who have recently inhaled cannabis.  One recent trial of 12 heavy and 12 occasional cannabis consumers administered oral doses of THC determined: '[C] "
"In addition, the number of participants who were scored as impaired on overall HGN was higher when THC was consumed together with alcohol, than in the THC only condition. This is somewhat consistent to the findings of Bosker et al. (2012), who observed an increase in HGN when THC was administered with 0.7 mg/ml alcohol (28 % positive) than when consumed alone (15 %). However, when THC was combined with 0.5 mg/ml alcohol , the presence of HGN was lowered (11 %) in their sample of heavy THC users who attended the study already under the influence of THC at each baseline (average baseline THC level was 7.1 ng/ml), and displayed no HGN at baseline. "
[Show abstract][Hide abstract] ABSTRACT: Rationale:
Cannabis and alcohol are the most popular drugs amongst recreational users and most prevalent in injured and deceased drivers. The Standardized Field Sobriety Tests (SFST) are commonly used to establish impairment due to drugs and alcohol, but limited empirical evidence exists concerning the combined effects of these drugs on SFST performance.
The sample comprised 80 individuals (31 females; 49 males). Age ranged between 21 and 35 years (M = 26.5, SD = 5). Forty participants (15 females; 25 males) took part in the low alcohol condition (BAC, <0.05 %), and 40 participants (16 females; 24 males), took part in the high alcohol condition (BAC, >0.05 %). For each part of the study, two levels of ∆9-tetrahydrocannabinol (THC) were administered (1.8 and 3 % THC) or a matching placebo cigarette (0 % THC) in combination with alcohol. Performance on the SFST was assessed 30 min post-dosing.
A number of significant differences in SFST performance were identified with 28 % of the sample failing the test (when the head movement and jerks sign was included) when low alcohol and low THC were administered together. When a higher dose of alcohol was administered with a low dose of THC, 38 % of the sample failed the test, and 35 % also failed when the high dose of alcohol was combined with a higher dose of THC.
The current results highlight the limited ability of the SFST to identify drug consumption in the absence of any evidence of driving impairment or physiological indicators.