Abstract
BACKGROUND: Several studies demonstrate the utility of Alcohol Monitoring Systems' (AMS) transdermal alcohol concentration (TAC) monitor to objectively quantify drinking. AMS standard criteria (i.e., TAC >0.02 g/dl) used for drinking detection are deliberately conservative, but consequently only detect drinking equivalent to 5 or more standard drinks. Our study sought to characterize the sensitivity of TAC measurement to detect low-level drinking defined as the consumption of 1 to 3 beers. METHODS: Data were pooled from 3 studies giving controlled doses of 1, 2, 3, 4, and 5 Corona© beers (12 oz = 0.92 standard units) to 32 male and 29 female research volunteers wearing TAC monitors under controlled conditions. Analyses describe the sensitivity to detect drinking at various peak TAC thresholds beginning with any positive reading >0 g/dl, and then using TAC thresholds of 0.02 and 0.03 g/dl. RESULTS: Nearly 40% of participants drinking 1 beer did not have a positive TAC reading. However, positive TAC readings were observed in more than 95 and in 100% of participants drinking 2 and 3 or more beers, respectively. The probability of peak TAC detection was a positive function of the number of beers consumed and a negative function of the minimum TAC threshold for detection. Drinking was somewhat more likely to be detected in females than males drinking 2 to 5 beers, but not after 1 beer. Use of AMS standard criteria only reliably detected the consumption of 5 beers, and 45.9% of all occasions of drinking 1 to 3 beers were undetected using 0.02 g/dl as a threshold. CONCLUSIONS: Peak TAC levels between 0 and 0.02 g/dl must be considered to detect the low-level drinking of 1 to 3 standard drinks, and such thresholds are necessary when researchers and clinicians want to detect low-level drinking.