False-positive results with an alcometer device

We write to report false-positive results with an alcometer device (Lion S-D2 brand) when it is used in the vicinity of recently applied alcohol disinfectant hand rub.

The Orchard Clinic is a medium secure forensic unit set within the grounds of the Royal Edinburgh Hospital. The use of an alcometer is essential in the treatment of Scottish government ‘restricted’ patients or if there is suspicion or evidence of alcohol misuse. Indeed, all staff receive training on the use of the alcometer during their induction period.

Recently a patient with ‘restricted’ status returned from leave outwith the clinic. On the patient's return they were breathalysed. The alcometer gave a reading of 0.04 mg/lBrAC – equivalent to just under one unit of alcohol. The patient denied consuming alcohol. Staff had used an alcohol-based hand disinfectant lotion prior to carrying out the test. This was consistent with hand hygiene guidelines following the H1N1 flu pandemic.

We later reproduced the positive alcometer results after using alcohol hand lotion in the standard way. The reading rose from 0.01 mg/lBrAC (background reading) to 0.1 mg/lBrAC – equivalent to two units of alcohol.

The alcohol hand rub used within NHS Lothian is up to 80% alcohol, which is one of the highest on the market. ¹ It is therefore likely there is much alcohol in the vapour around where it is used. When the individual inhales prior to the test, some alcohol vapour is also taken in which is exhaled back into the instrument as part of their sample.

False-positive alcometer results may have serious implications for the treatment of forensic patients. No other report of alcohol hand lotion raising alcometer readings was found in the literature. It had not been reported as an issue with local colleagues in the Alcohol Problem Service or with Lothian and Borders Police. However, it is recognised that the police may carry out the test in a more open environment than a ward treatment room.

In addition to reporting this finding to the manufacturer, the local procedure for operating the alcometer has now been amended to ensure that alcohol hand lotion: (a) is not used by any staff involved in taking an alcometer reading at least 5 min before taking the test; and (b) is not used in the same room at least 5 min before a test is carried out.

Staff are encouraged to use soap and water to clean their hands before administering an alcometer test.