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2013 Annual Meeting

2013 NAPCRG Annual Meeting

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HD12 Assessing Accuracy of Personal Breathalysers and Self-Estimated Alcohol Consumption for Driving Decisions

Susannah Fleming, MEng, DPhil; Elizabeth Spencer, MMedSci, PhD; Richard Stevens, BA, MSc, PhD; Matthew Thompson, BSc, MBChB, MPH, DPhil; Helen F Ashdown, MA, BMBCh

11/10/13 2:00 PM - 3:00 PM Governor General II

Context: Driving accidents cause 1.2 million deaths each year worldwide, with alcohol a causative factor in at least one fifth. Health promotion in many primary care and community settings therefore emphasises reducing or avoiding driving after drinking alcohol. Breathalysers measure breath alcohol and can estimate whether someone is over the legal driving limit. Cheap breathalysers are now available for sale to the public from pharmacies; however consequences of inaccurate readings are potentially considerable. Objective: To determine the diagnostic accuracy of personal breathalysers Design: Diagnostic accuracy study Setting: Licensed bars in Oxford, United Kingdom Participants: 208 participants aged 18 or over who had consumed alcohol Instrument: Three personal breathalysers (two single-use and one digital multi-use) compared with a police breathalyser, used in a randomised order Outcome Measures: Diagnostic accuracy for detection of alcohol levels at or over the UK/US driving limit (35 µg/100ml breath or 80 mg/100ml (0.08%) blood alcohol concentration), using the police breathalyser as reference standard. We also calculated diagnostic accuracy of self-reported alcohol consumption. Results: 38/208 (18.3%) of participants were at or over the driving limit according to the police breathalyser. The digital multi-use and one of the two single-use devices had a sensitivity of 89.5% (95% CI 75.9-95.8%) and 94.7% (95% CI 75.4-99.1%), with specificity of 64.1% (95% CI 56.6-71.0%) and 50.6% (95% CI 40.4-60.7%) respectively. The other single-use device had a sensitivity of 26.3% (95% CI 11.8-48.8%) and a specificity of 97.5% (95% CI 91.4-99.3%). Self-reported alcohol consumption of 5 UK units or fewer had a higher sensitivity than all personal breathalysers. Conclusions: While two of the breathalysers tested had good sensitivity, one had very poor sensitivity – all were less sensitive than self-reported alcohol consumption. Primary care clinicians should be aware that over-the-counter diagnostic devices such as these may not always be fit for purpose.