London, Dec 21 (IANS): Researchers have found that the ability of some breathalysers, widely sold to the British public to detect potentially unsafe levels of alcohol in blood while driving, varies considerably.

The findings 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 of three personal use breathalysers to detect alcohol levels in blood in 208 adults.

These adults were drinking in college bars and pubs in Oxford.

Twenty minutes after drinking, participants were asked to test the single use Alcosense Single, the comparable Drager Alco-check as well as the digital multi-use Alcosense Elite breathalyzer - the three devices easily available in the market.

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.

Compared with the police breathalyser, the digital Alcosense Elite had a sensitivity of around 90 percent while the Drager AlcoCheck had a sensitivity of just under 95 percent.

The Alcosense Single had an even lower sensitivity of only 26 percent meaning that the device would pick up only around one in four people over the legal limit, shortly after drinking.

"Even a sensitivity of 95 percent means that around one in 20 people over the legal driving limit for alcohol would be falsely reassured," the authors said.

"The research suggests that some personal breathalysers available for sale to the public are not always sufficiently sensitive to test safety to drive after drinking alcohol," they wrote in a paper appeared in the online journal BMJ Open.