Ozga‐Hess 2019.

Study characteristics
Methods	Design: RCT Recruitment: Cigarette smokers were recruited from the community via fliers, online postings, and word of mouth Setting: Morgantown, West Virginia, USA Study start date: Not reported. Study end date: Not reported
Participants	Total N: 60; E‐cigarette plus own brand = 30. Own brand cigarette (control) = 30 38.3% female; mean age completers 35.1 (SD 11) (N = 34) non‐completers 36.8 (SD 12.9) (N = 26); mean cpd completers 16.7 (SD 4.9), non‐completers 19.6 (SD 6.1); mean FTND completers 5.3 (SD 1.8), non‐completers 5.9 (SD 1.9) Inclusion criteria: 18 to 60 years of age; smoking ≥ 10 cigarettes per day for ≥ 1 year exhaled air carbon monoxide (CO) level of ≥ 10 ppm (Micro+™ basic monitor; CoVita; Haddonfield, NJ) Contemplation or Preparation Stage of Change (indicating interest in a quit attempt within the next 1 ‐ 6 months) Exclusion criteria: reported chronic health or psychiatric conditions past month use of marijuana ≥ 5 days past month use of any other illicit drugs, or regular use of ECIGs or other tobacco products (i.e. ≥ 1 day per week) individuals in the Precontemplation (no interest in quitting) or Action (actively trying to quit) Stage of Change currently breast‐ feeding or tested positive for pregnancy via urinalysis
Interventions	EC: Refillable E‐cigarette (18 mg/ml ) plus own brand cigarette. Kanger mini Protank‐II, which is a 1.5 ml Pyrex glass tank with a drip tip and atomizer head coils (KangerTech; China), and a 3.3 V constant output, 900 mAh, eGo‐T battery (Joyetech; Irvine, CA). The liquid (The Vapor Room, Sky Vapors LLC, Frostburg, MD) was labeled as 70% propylene glycol and 30% vegetable glycerin, with a nicotine concentration requested of 18 mg/ml. Participants could choose tobacco, menthol or wild berry flavor and could switch between sessions. Ad libitum use for 4 weeks Own brand cigarette ad libitum use for 4 weeks
Outcomes	Daily for salivary cotinine samples. Daily self‐monitoring device to log e‐cigarette and cigarette use. Collected used cigarette filters Weekly CO breath test Attended the laboratory weekly for assessments (Days 8, 15, 22, and 29). Then completed a follow‐up visit 1‐month post‐intervention self‐reported withdrawal symptoms Reported experience of specific symptoms rated using a visual analog scale with a range from 0 (not at all) to 100 (extremely). e.g. craving, irritability, dry mouth, throat irritation, and cough
Study funding	Financial support provided to MDB and GAD by WVU Senate Grant for Research, and to GAD, MDB, and NAT by Cooperative Agreement Number 1‐U48‐DP‐005004 from the Centers for Disease Control and Prevention (CDC) to the West Virginia Prevention Research Center. Support provided to NJF and JEOH by the National Institute of General Medical Sciences (NIGMS T32 GM081741). Additional support provided by WV Tobacco Cessation QuitLine
Author declarations	Author SGF has consulted for various pharmaceutical companies on matters relating to smoking cessation. All other authors declare that they have no conflicts of interest
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "Using a simple randomized design" Comment: not adequately explained
Allocation concealment (selection bias)	Unclear risk	Not adequately described in the paper
Blinding of participants and personnel (performance bias) All outcomes	High risk	Participants and investigators were not blind
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Biochemical validation
Incomplete outcome data (attrition bias) All outcomes	High risk	40% retention, but no difference between groups
Selective reporting (reporting bias)	Low risk	All outcomes reported