Table 4

Risk of bias assessment for the randomised controlled trials

Author, yearWas the randomisation sequence adequately generated?Was allocation adequately concealed?Was there blinding of participants?Was there blinding of caregivers?Was there blinding of data collectors?Was there blinding of statistician?Was there blinding of outcome assessors?Was loss to follow-up (missing outcome data) infrequent?*Are reports of the study free of suggestion of selective outcome reporting?Was the study apparently free of other problems that could put it at a risk of bias?
Randomised controlled trials assessing ENDS vs ENNDS
 Bullen, 201334–39Definitely yesDefinitely yesDefinitely yesDefinitely yesDefinitely yesDefinitely yesDefinitely yesDefinitely noDefinitely yesDefinitely yes
 Caponnetto, 201325Definitely yesDefinitely yesDefinitely yesDefinitely yesDefinitely yesDefinitely yesDefinitely yesDefinitely noDefinitely yesDefinitely yes
Randomised controlled trials assessing ENDS vs other quitting mechanisms
 Adriaens, 201433Definitely yesProbably noProbably noProbably noProbably noProbably noProbably noDefinitely noProbably yesProbably yes
 Bullen, 201334–39Definitely yesDefinitely yesDefinitely noDefinitely noProbably yesProbably yesDefinitely yesDefinitely noDefinitely yesDefinitely yes
  • All answers as: definitely yes (low risk of bias), probably yes, probably no, definitely no (high risk of bias).

  • *Defined as less than 10% loss to outcome data or difference between groups less than 5% and those excluded are not likely to have made a material difference in the effect observed.

  • ENDS, electronic nicotine delivery systems; ENNDS, electronic non-nicotine delivery systems.