Kumral 2016.

Study characteristics
Methods	Design: Prospective randomized clinical trial Recruitment: All patients admitted to a smoking cessation clinic at the Department of Otorhinolaryngology‐Head and Neck Surgery, Okmeydanı Training and Research hospital Setting: Smoking cessation clinic, Turkey Study start date: March 2013; Study end date: November 2013
Participants	Total N: 98 but analysis excludes 16 from intervention and 10 from control who did not stop smoking; thus 72 analyzed N per arm: EC: 58 (42 ana lysed); Non‐EC 40 (30 ana lysed) Inclusion criteria: Smoked at least one pack of cigarettes a day for at least 5 years. Exclusion criteria: History of allergic rhinitis, chronic sinusitis, vasomotor rhinitis, asthma, malignancy, or surgery in upper respiratory tract; Age under 18; Use of psychoactive drugs Inclusion based on specific population characteristic: No 44% women; mean age 36; mean cpd and mean FTND not specified Motivated to quit: “All patients were willing to quit smoking” E‐cigarette use at baseline: Not specified
Interventions	EC: Unclear EC arm: “used EC to quit smoking” – allowed to select brand and flavor, used “medium density” liquid (11 ‐ 12 mg/ml) (no further detail given) Non‐EC arm: Received cognitive behavioral therapy (no further detail given)
Outcomes	3 Months Sino‐nasal outcome test (SNOT‐22) via self‐administered questionnaire, to evaluate changes in subjective symptoms. Saccharin transit test to evaluate nasal mucociliary clearance (MCC) function which authors state is “an important defence mechanism”
Study funding	Not specified
Author declarations	Not specified
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: “Patients participating in the study were randomly divided into two groups; EC smokers (group 1) and non‐EC smokers (group 2).” No further detail provided
Allocation concealment (selection bias)	Unclear risk	No information given
Blinding of participants and personnel (performance bias) All outcomes	High risk	Participants were not blinded. The trial is described as single‐blinded and outcome assessors were blinded. No placebo used
Blinding of outcome assessment (detection bias) All outcomes	High risk	Self‐reported outcome data, participants not blinded and unequal amounts of support between arms
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Dropout rate not clear. Only ana lysed people who quit
Selective reporting (reporting bias)	Low risk	All expected outcomes reported