The Cochrane review of electronic cigarettes for smoking cessation: Remaining focused on the evidence

We are grateful for the opportunity to reply to the commentary on our Cochrane review of electronic cigarettes (EC) for smoking cessation [1] posed by Pisinger and Vestbo [2] with subsequent commentary by McAlinden et al. [3].

Below we list the issues raised and provide our responses.

The decision to include two studies where nicotine levels were judged to be very low as non-nicotine EC was flagged as unusual. This decision was based on what was considered to be a clinically meaningful nicotine concentration (i.e. one that might have an effect, as an active ingredient). Lee et al. [4] used an EC with a nicotine concentration of 0.01 mg·mL−1 and van Staden et al. [5] used a device with 0.014 mg·mL−1 of nicotine, i.e. concentrations that are unlikely to have any detectable psychoactive effects. Only the study of Lee et al. [4] was suitable for inclusion in the efficacy analysis. For the purpose of this letter, we conducted a post hoc sensitivity analysis that includes this study in the nicotine EC group (figure 1). The results still show a clinically and statistically significant benefit of EC compared to nicotine replacement therapy (NRT), but statistical heterogeneity has increased (from I2 of 0% without Lee et al. [4], to 58% with).