Has your drink been spiked? DIY tests may not tell the truth

Many positive results produced by the kits are false, says new report

By Roger Dobson
Thursday 20 October 2011 13:32

Drink-spike testing kits have been found to offer little or no protection because they don't work properly, researchers will reveal this week. Many positive results produced by the two types of kit tested were false, they say. One test wrongly identified one in four drinks as being spiked.

No accurate data exists on the number of drink-spiking incidents in the UK each year. Last week Chenai Zinyuku, a contestant on The X Factor television show, reported that her drink was laced with a date-rape drug when she visited a nightclub in Leeds.

Notwithstanding the seriousness of her case, researchers warn that the high number of false positive results may lead to exaggerations about the scale of the drink spiking. False negative results may also lead to drinkers being wrongly reassured.

"Use of drug-detector kits by the public in the night-time environment needs further investigation and may create a false sense of security and undue concern among kit users,'' the researchers, from the Centre for Public Health at Liverpool John Moores University, will say.

"Results suggest that it is possible that some members of the public have used these kits and obtained a false positive result, adding further to the confusion and concern regarding the true magnitude of drink spiking within the UK.

"Neither kit tested here demonstrated high levels of sensitivity, specificity or utility under these specific laboratory protocols.... Drug-facilitated sexual assault does occur and is a horrific event, but the role that testing kits can play in reducing these crimes is limited, while what they can detect is unclear, their detection rate is poor and many positive tests are false positive results.''

In the research, reported in the journal Addiction, the researchers looked at two tests on the market for DIY drink testing. Drugs investigated were gamma hydroxybutyrate (GHB), ketamine, temazepam, flunitrazepam and diazepam.

Each kit was tested 10 times for each drink and drug or placebo combination. The results show that with one of the kits, a drug was correctly detected in only 69 per cent of tests. Researchers also found that the sensitivity of the kits was affected by the type of drink in which they were tested. The ability of one kit to identify the presence of drugs in beer was poor, with a sensitivity of 37 per cent.

"For kits to be effective public health tools, the public must be as confident in their reliability as they are in ... for example, pregnancy testing kits,'' says the report. "Due to the infrequent occurrence of drink spiking, and because most drinks tested are likely to be drug free, positive results are more likely to be false positives. Such results have major social and commercial implications if individuals are suspected incorrectly of being a perpetrator, and ... venues are perceived incorrectly to be places where such behaviour occurs.''

The report says it is important drink spiking be put in context: "The most comprehensive UK-based study reported that only 21 of the 1,014 alleged drug-facilitated sexual assault cases were attributed to involuntary ingestion of a drug." This included three cases where the drug was ecstasy, which reduces inhibition, but does not induce sedation.

It says, with one kit, raters recorded false positives for benzodiazepines in 26.3 per cent of tests. And it adds: "We suggest the limited resources available to protect sexual health in night-time environments be used to tackle well-established public health issues [such as]the role of excessive alcohol consumption in sexual assaults, brief ill-conceived sexual encounters, the rising prevalence of sexually transmitted infections and unwanted pregnancies.''

In a response to the research, one of the kit makers says: "We accept that test kits are not foolproof, but we believe strongly that they play an active role in increasing consumer awareness about the dangers of drink spiking. We recommend that consumers always discard a drink they consider suspicious, even if the test proves negative."

The kit maker adds: "We do not agree with the authors that consumers will overestimate their personal risk due to a false positive result.''