Blood test for smokers could show best way to quit

15 January 2015

A blood test could optimise treatment choice for individual smokers, giving them greater success at quitting, research in The Lancet Respiratory Medicine suggests. The blood test would measure how quickly an individual breaks down nicotine inside their body, which is known as the nicotine-metabolite ratio (NMR) – a genetically informed biomarker


Previously, research has found that people who break down nicotine faster are more likely to smoke more, and can find it more difficult to stop smoking. Smokers crave cigarettes when nicotine levels in their blood drop below a certain level, current treatments counteract this craving. The new findings could aid people in choosing whether to use nicotine patches or non-nicotine therapy medication to gain success.

The research, part of the largest ever study to look at how genetic differences affect tobacco dependence and quitting, involved 1246 participants including similar numbers of ‘normal’ and ‘slow’ metabolisers of nicotine. Participants were randomly assigned to an 11 week treatment involving either a nicotine patch and placebo pill, varenicline (non-nicotine replacement therapy drug) pill and placebo patch, or placebo pill and patch; all in addition to behavioural counselling. 

The headline finding at the end of the treatment was that normal metabolisers (60% of the population) were twice as likely to successfully stop smoking when they used the non-nicotine replacement therapy drug varenicline than the the nicotine patch. Further, normal metabolisers having varenicline were still more likely to be abstaining 6 months later.  

Slow metabolisers had no significant difference in success rates for the two different treatments, varenicline and nicotine patches, but were more likely to experience side-effects with varencicline than normal metabolisers. Dr Rachel Tyndale, co-lead author said the data suggested treating ‘normal’ metabolisers with varenicline and ‘slow’ metabolisers with the nicotine patch to maximise rates of smoking cessation whilst minimising side effects.

In a linked comment article, Jennifer Ware, Neil Davies and Marcus Munafo, from the University of Bristol, observed: “The results…are an important scientific advance. Should the findings be replicated, they might lead to changes in clinical practice through the implementation of prescriptions stratified on the basis of a biomarker test”.

Importantly though, they caution that (in addition to independent replication of the findings) a full health economic assessment of such a test would need before any implementation in clinical practice.

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