Field and laboratory alcohol detection with 2 types of transdermal devices

Two types of transdermal electrochemical sensors that detect alcohol at the skin surface were evaluated. One, the AMS SCRAM device, is locked onto the ankle and is based on a fuel cell sensor; the other, a Giner WrisTAS device, worn on the wrist, is based on a proton exchange membrane. SCRAM is used by several court systems in the United States to monitor alcohol offenders, WrisTAS, a research prototype, is not commercially available.

The 2 devices were worn concurrently by 22 paid research subjects (15 men, 7 women), for a combined total of 96 weeks. Subjects participated in both laboratory-dosed drinking to a target of 0.08 g/dl blood alcohol concentration (BAC), and normal drinking on their own; all subjects were trained to use and carry a portable fuel-cell breath tester for BAC determinations. Overall 271 drinking episodes with BAC > or = 0.02 g/dl formed the signal for detection-60 from laboratory dosing, and 211 from self-dosed drinking, with BAC ranging from 0.02 to 0.230 g/dl (mean 0.077 g/dl).

False negatives were defined as a transdermal alcohol concentration response equivalent <0.02 g/dl when BAC > or = 0.02 g/dl. The overall true-positive hit rate detected by WrisTAS was 24%. The low detection rate was due to erratic output and not recording during nearly 67% of all episodes; reportedly a chipset, not a sensor problem. SCRAM correctly detected 57% across all BAC events, with another 22% (total 79%) detected, but as <0.02 g/dl. When subjects dosed themselves to BAC > or = 0.08 g/dl, SCRAM correctly detected 88% of these events. SCRAM devices lost accuracy over time likely due to water accumulation in the sensor housing. Neither unit had false-positive problems when true BAC was <0.02 g/dl.

Each device had peculiarities that reduced performance, but both types are able to detect alcohol at the skin surface. With product improvements, transdermal sensing may become a valuable way to monitor the alcohol consumption of those who should be abstaining.