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Personal breathalysers may give false reassurance to drivers, research shows

BMJ 2014; 349 doi: http://dx.doi.org/10.1136/bmj.g7745 (Published 23 December 2014) Cite this as: BMJ 2014;349:g7745
  1. Jonathan Gornall
  1. 1Suffolk

Researchers who tested three types of personal breathalysers on drinkers in bars in Oxford city centre found widely different levels of accuracy that they say “could have catastrophic safety implications for drivers” who rely on the devices to decide whether they are fit to drive after drinking.

The researchers, from the Nuffield Department of Primary Care Health Sciences at the University of Oxford, tested the diagnostic accuracy of two single use disposable breathalysers and one multi-use digital device against results obtained from a Home Office approved breathalyser used by police for roadside testing.

In a paper published today on BMJ Open the researchers reported that the relative accuracy of the three breathalysers varied from 26% to 95%, which in the case of the worst performing device meant that as many as “three people in four . . . are falsely reassured when over the limit.” 1

Earlier this month Dorset Police advised motorists not to rely on personal breathalysers, after county trading standards officers tested 14 devices and found that nine falsely assured users that they were safe to drive. Ivan Hancock, trading standards service manager for Dorset County Council, said, “Drivers would be extremely foolish to rely on the readings they get from one of these cheap devices.”2

The Oxford findings are particularly relevant at this time of year, at the height of the police’s seasonal drink driving campaigns—and even more so in Scotland, where on 5 December the drink driving limit was reduced from 80 mg to 50 mg of alcohol in every 100 mL of blood, bringing the country into line with the rest of Europe.

The researchers set out to test the devices in a “real world situation, representing one possible application …

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