Immediate, quantitative estimation of blood alcohol concentration from saliva

Objective: Reliable, valid, and noninvasive methods to quantitatively estimate blood alcohol concentration (BAC) are important in forensic, work place, medical and research settings. To date, noninvasive methods for quantitatively estimating BAC have primarily used breath testing. This study evaluated a new device for estimating BAC via saliva that is unique in providing on-the-spot, quantitative results in 2 minutes. The Q.E.D.®-A150 test (STC Technologies, Inc., Bethlehem, Pa.) is based on the enzymatic oxidation of alcohol by alcohol dehydrogenase. Saliva alcohol concentration (SAC) is read directly from the test device. Method: In each of three sessions, 24 male and 15 female social drinkers, aged 21-28 years, provided yoked breath and saliva samples prior to, and at five times following, a dose of 1.0 g (men) or 0.9 g (women) alcohol per kg lean body mass. Results: Intertest reliability, determined by two simultaneous saliva samples, was very high for each measurement time (r's = .97 to .99), for each subject (r's = .95 to .99) and across all observations (r = .98). The coefficient of variation was below 5% in 97% of paired observations. The correlation between breath and saliva estimates was .94 across all observations and ranged from .92 to .98 across measurement times. The difference between breath and saliva estimates was significantly larger on the ascending limb than on the descending limb of the blood alcohol curve at comparable BACs. On the average, SAC estimates were 6 mg/dl higher than breath during ascending BACs and 3 mg/dl higher than breath during descending BACs. Individual differences in the ratio of SAC to breath measures of BAC ranged from 0.99 to 1.15 (average = 1.06). Test performance was not affected by gender, drinking pattern or cigarette smoker status. Conclusions: The Q.E.D.®-A150 device had good reliability and validity for the noninvasive, quantitative estimation of BACs.