Polosa 2014a

Methods	Design: Retrospective cohort (retrospective audit of clinical records) Recruitment: Review of medical records from a respiratory outpatient clinic in Italy from September 2012 until December 2013 Setting: Respiratory outpatient clinic, Italy Inclusion criteria: People with mild to moderate asthma reporting regular EC use on at least 2 consecutive follow‐up visits Exclusion criteria: None reported
Participants	Total N: 18, 39% (N = 7) women 10 were using EC only (3 women, mean age 36) 8 used ECs and smoked ≤ 5 cpd (4 women, mean age 42) Both groups smoked 22 cpd at baseline Duration of EC use 10 ‐ 14 months. N = 12 using them for > 1 year All started on 1st generation EC, but the 'majority' switched to a 'personal vaporiser' (2nd or 3rd generation)
Interventions	Observational; no specific intervention. First 2 observations prior to EC use, second 2 observations during EC use
Outcomes	Data from 4 clinic visits were collected: (1) pre‐baseline (6 – 12 months prior to baseline); (2) baseline; (3) 6 (± 1) month follow‐up; and (4) 12 (± 2) month follow‐up. Visits 1 and 2 were pre‐EC use and visits 3 and 4 were during EC use At each visit, participants were assessed by clinical history and examination and re‐evaluation of treatment adherence and efficacy Juniper’s Asthma Control Questionnaire (ACQ) score Number of exacerbations from the previous follow‐up visit (defined as an increase in respiratory symptoms requiring a short course of oral or parenteral corticosteroids) Forced expiratory flow in 1 second (FEV1) Forced vital capacity (FVC) Expiratory ratio (% FEV1/FVC) Forced expiratory flow at the middle half of the FVC (FEF 25 ‐ 75%); Bronchial provocation tests assessing Airway HyperResponsiveness (AHR) with methacholine (some participants only)
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	High risk	Retrospective cohort
Allocation concealment (selection bias)	High risk	Self‐selected sample
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Although there is no blinding, the study design and lack of intervention means that there is unlikely to be significantly impact on performance
Blinding of outcome assessment (detection bias) All outcomes	High risk	No biochemical validation undertaken
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Not applicable; unclear if some participants attended first 3 visits but not 4th, and hence were excluded
Selective reporting (reporting bias)	Unclear risk	Unable to determine prespecified outcomes