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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"HGN refers to the involuntary jerking or sudden movement of the eye that naturally occurs when the eyes gaze to the side. In unaffected individuals, HGN occurs when the eye gaze is at high periphery angles; however this occurs at lesser angles when an individual is impaired by alcohol or drugs (Bosker et al., 2012). This test requires participants to focus on and follow the trajectory of a slow moving horizontal object which is presented directly in front of their face (usually a pen). "
[Show abstract][Hide abstract] ABSTRACT: Objective:
The Standardized Field Sobriety Tests (SFST) are utilised widely to assess fitness to drive when law enforcement suspects a driver's ability to drive is impaired, whether by drugs or alcohol. The SFST ostensibly achieve this through assessment of the level of drivers' cognitive and psychomotor impairment, although no studies have explicitly assessed the relatedness of cognitive ability and performance on the SFST. The current study aimed to assess the relationship between the three components of the SFST with a well validated computerised cognitive battery.
A sub-set of 61 placebo condition participants comprised the sample, with 33 females and 28 males (mean age 25.45 years). Correlations between the individual SFST subscales 'Horizontal Gaze Nystagmus' (HGN), the 'One Leg Stand' (OLS) and the 'Walk and Turn' test (WAT) and Cognitive Drug Research (CDR) sub-scales of 'Quality of Working Memory', 'Power of Attention' and 'Continuity of Attention' were analysed using point-biserial correlation.
Sixty participants were included for analyses. A weak-moderate positive (five subscales) and a moderate-strong negative (two subscales) association was noted between seven of the nine individual CDR subscales and the SFST subscale of the WAT test (all p<0.05). Individually, a moderate positive association was noted between the sub-scale 'Nystagmus lack of smooth pursuit' and 'digit vigilance reaction time' and 'choice reaction time; reaction time' (both p<0.05) and 'Nystagmus head move and/or jerk' and 'simple reaction time' (p<0.001). When assessed as a partially composite factor, a comparable association was also noted between the composite score of the SFST subscale 'Nystagmus head move and/or jerk' and both (a) simple and (b) digit vigilance reaction time (both p<0.05). No association was noted between any of the individual cognitive variables and the SFST subscale 'OLS', or between composite cognitive scores 'Quality of Working Memory', 'Power of Attention' and 'Continuity of Attention' and total SFST scores.
Variation in some aspects of cognitive performance was found to be moderately and positively correlated with some individual aspects of the SFST; particularly among tasks which assess reaction time. Impairment of these cognitive processes can also contribute to the completion of complex tasks such as driving or the SFST. Complex behavioural tasks such as driving are often severely impaired due to intoxication, and thus in a practical sense, the SFST can still be considered a useful screening tool to identify drug or alcohol impaired drivers.
"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] "