Tanew 1991.

Study characteristics
Methods	RCT, placebo‐controlled, double‐blind Date of study: not stated Location: 2 centres in Austria (Vienna, Innsbruck)
Participants	Randomised: 60 participants (mean age 40 years (acitretin), 49 years (placebo); 42 male) Inclusion criteria Participants with moderate‐severe psoriasis (BSA ≥ 20), age ≥ 18 years Exclusion criteria Not stated Dropouts and withdrawals 12/60 (20%) Time and reasons: acitretin group (7): severe muscle pain (1), serum triglycerides exceeding 400 mg/dL (2), irregular drug intake (4) placebo group (5): unrelated to therapy
Interventions	Intervention A. Acitretin (n = 30), orally, 1 mg/kg, daily, 12 weeks or until complete clearing Control intervention B. Placebo (n = 30), orally, daily, 12 weeks Co‐intervention PUVA, phototherapy, 4 times/week, 12 weeks
Outcomes	Assessments at 12 weeks Primary and secondary outcomes of the trial Not defined Outcomes of the trial Complete remission Side effects
Notes	Funding: supported by a grant from Hoffma La Roche & Co Ltd Declarations of interest: not stated
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote (p 682): "Only patients ... were included and assigned randomly..." Comment: no description of the method used to guarantee random sequence generation
Allocation concealment (selection bias)	Unclear risk	Quote (p 682): "Only patients ... were included and assigned randomly..." Comment: no description of the method used to guarantee allocation concealment
Blinding of participants and personnel (performance bias) All outcomes	High risk	Quote (p682): "Acitretin ... or placebo..." Comment: no description of the method used to guarantee blinding of participants and personnel as acitretin leads to visible adverse effects (cheilitis)
Blinding of outcome assessment (detection bias) All outcomes	High risk	Quote (p682): "Acitretin ... or placebo..." Comment: no description of the method used to guarantee blinding of participants and personnel as acitretin leads to visible adverse effects (cheilitis)
Incomplete outcome data (attrition bias) All outcomes	High risk	Randomly assigned 60, analysed 48 Quote (p 683): "Of the 60 patients, 48 completed the study and were included in the statistical analysis" Comment: not ITT
Selective reporting (reporting bias)	Unclear risk	No protocol available, no outcomes defined in the Method section