Home alcohol tests give conflicting results in Yle trial

Yle tested two inexpensive home alcohol tests and found that one detected alcohol while the other showed no alcohol after a journalist had drunk wine.

The tests, sold in pharmacies and shops, are intended to indicate whether someone is under the influence of alcohol and, if so, how much alcohol is in their system. Many people use them to assess whether they can drive after drinking without exceeding the drink-driving limit.

For the test, the journalist drank 16 centilitres of white wine over about 30 minutes at a bar. The first test, the Co-Test Alkotest, measured alcohol in exhaled air and indicated about 0.2 per mille. Reading the result required comparing the colour of the sample with a colour scale on the breath tube.

The Medigoo Alcohol Test, which uses saliva, did not appear to detect any alcohol. The indicator stick did not change colour after being dipped in saliva. The test was repeated immediately using the second test in the package, with the same zero result.

Yle also asked senior police superintendent Ari Järveläinen to conduct a breath test on the journalist at a bar in Helsinki. The police breathalyser showed 0.06 milligrams of alcohol in exhaled air, corresponding to about 0.13 per mille.

The drink-driving limit is 0.22 milligrams of alcohol in exhaled air, or 0.5 per mille. More than 30 minutes had passed between the first home test and the police test, so some of the alcohol had already left the body. However, the police result was consistent with the first home test, meaning the saliva test would also have been expected to detect alcohol.

Police warn against relying on home tests

Based on the limited trial, home alcohol tests can be significantly inaccurate. They require precise timing and interpretation of colour codes, creating opportunities for user error.

Police do not recommend using home tests to decide whether it is safe to drive.

There is always a risk that a test will fail or give an incorrect result, Järveläinen said. An accident could then occur, followed by potentially serious consequences.

More than one-third of drivers involved in fatal crashes have been under the influence of intoxicants, with alcohol the most common substance. Police continue to advise: if you drink, do not drive.

Drivers do not commonly cite home alcohol tests when stopped for a roadside breath test, and referring to such a test does not remove responsibility. Järveläinen said it was more common for drivers to play down how much alcohol they had consumed.

The packaging of the first test used in the trial clearly warned that its result could not be used as evidence that a driver was or was not intoxicated or under the influence of alcohol. It also said the result could not be used to challenge tests carried out by police or at their request.

The instructions for the second test said only that the saliva alcohol test provided a preliminary result and was intended for informational use.

Tests require precise timing

For both tests, the result had to be read a specified number of minutes after the sample was taken. In a busy bar or while hungover, users may not monitor the timing accurately, or they may skip reading the instructions. Errors by the user can make the results unreliable.