Ye 2020.

Study characteristics
Methods	RCT, active‐controlled study Date of study: August 2017 to February 2019 Location: China
Participants	Randomised: 150 participants Inclusion criteria Patients who met the diagnostic criteria for psoriasis vulgaris Patients who had no other skin system diseases patients who co‐operated with the treatment Patients whose clinical data were complete Exclusion criteria Patients who were allergic to or unsuitable for the treatment Patients who had undergone systemic psoriasis treatment within the previous weeks; patients who had received glucocorticoids or formic acid immunosuppressants within the previous two weeks Patients who had congenital immunodeficiencies in addition to psoriasis Baseline characteristics N = 150, mean of age 33 years, and 57% men Dropouts and withdrawals Not stated
Interventions	Intervention A. Acitretin per os initial dose 30 mg/d Control intervention B. No treatment Co‐intervention: narrow‐band ultraviolet therapy
Outcomes	At week 8 Primary outcomes Basic recovery (patients with PASI score reduction between 60% and 89%) Significant improvement (patients with PASI score reduction over than 90%: "good curative effect") Improvement (patients with PASI score reduction between 20% and 59%) Ineffectual treatment (patients with PASI score reduction less than 20%) Secondary outcomes Recurrence within 1 year after the treatment (patients were notified to revisit the clinic by telephone)
Notes	Funding source: not stated Declarations of interest: Quote (p 5074): "None"
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote (p 5069): "The patients were randomly divided into the control group (n = 75) and the observation group (n = 75)." Comment: no description of the method used to guarantee random sequence generation
Allocation concealment (selection bias)	Unclear risk	Quote (p 5069): "The patients were randomly divided into the control group (n = 75) and the observation group (n = 75)." Comment: no description of the method used to guarantee allocation concealment
Blinding of participants and personnel (performance bias) All outcomes	High risk	Comment: no description of whether the trial is blinded or open
Blinding of outcome assessment (detection bias) All outcomes	High risk	Comment: no description of whether the trial is blinded or open
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Randomised 150, analysed 150 Comment: methods for dealing with missing data not specified, ITT analysis
Selective reporting (reporting bias)	Unclear risk	Comment: no protocol was available. The prespecified outcomes mentioned in the Methods section appeared to have been reported.