London: The ability of some breathalysers widely sold to the UK public to detect potentially unsafe levels of breath alcohol for driving, varies considerably, according to a new study.
The findings published in the journal BMJ Open call into question the regulatory process for approving these sorts of devices for personal use, say the researchers, particularly as false reassurance about a person's safety to drive could have potentially catastrophic consequences.
The researchers compared the diagnostic accuracy (sensitivity) of three personal use breathalysers to detect alcohol levels at or over the UK legal limit in 208 adults, who were drinking in college bars and pubs.
At least 20 minutes after drinking, participants were asked to test the single use Alcosense Single (100 people) or the comparable Drager Alco-check (108 people), as well as the digital multi-use Alcosense Elite, one minute apart, in random order.
These devices are widely available in leading pharmacies and other major retailers, as well as online.
The participants, whose average age was 20, estimated that they had drunk an average of 6 units of alcohol (46g) that evening, ranging from 1 to 25 units (8-204g).
The readings from the three devices were compared with those obtained from a Drager Alcotest 6510 device, which is used by the police to check drivers' legal alcohol limits at the roadside.
The legal limit for driving in the UK is 35 microgramme/100 ml of breath alcohol, and almost one in five (18 per cent) of those tested were at or over this limit, when the police breathalyser was used.
Compared with the police breathalyser, the digital Alcosense Elite had a sensitivity of around 90 per cent, while the Drager AlcoCheck had a sensitivity of just under 95 per cent, in the main analysis.
But even a sensitivity of 95 per cent means that around 1 in 20 people over the legal driving limit for alcohol would be falsely reassured, researchers said.
"We question whether even this would be sufficient sensitivity to assess safety to drive," they said.
And the Alcosense Single had an even lower sensitivity of only 26 per cent, compared with the police breathalyser, meaning that the device would pick up only around one in four people over the legal limit, shortly after drinking.
And when participants, rather than the researchers, interpreted the results of this device, the sensitivity fell further to 17 per cent, researchers said.