Beyond Quitting: Uncovering Gaps in Reporting Dual Use in Trials of E-Cigarettes for Smoking Cessation.

INTRODUCTION: Nicotine e-cigarettes (ECs) have been evaluated as aids for combustible cigarette (CC) cessation and in a recent evidence synthesis, were determined to improve quit rates versus nicotine replacement therapy (NRT). Dual EC/CC use is a common real-world tobacco use pattern with distinct dependence and harm exposure implications but is rarely treated as a trial outcome. METHODS: We reviewed peer-reviewed trials included in a recent Cochrane review and meta-analysis of EC for smoking cessation to determine whether dual EC/CC use prevalence at trial endpoints (1) was directly reported (or derivable from reported outcomes) and (2) the specificity with which dual use was defined. Further, we calculated the prevalence of dual use at the most commonly reported post-intervention timepoint (i.e., 4 weeks). RESULTS: Of 71 eligible peer-reviewed trials, 57 (80.3%) did not report dual use prevalence; 1 (1.4%) allowed derivation; and 12 (16.9%) reported dual use as an outcome. Only one of those twelve that reported dual use specified both the frequency and duration of use of each product in their definition of dual use. Across reported timepoints, dual use prevalence in EC arms ranged from 6.6% to 89.5%; the mean prevalence at 4 weeks was 42.6%. CONCLUSIONS: Dual use is infrequently and inconsistently reported in EC smoking cessation trials, limiting interpretation of both clinical efficacy and public health impact. We provide recommendations for defining dual use as a trial outcome and for standardizing reporting.