Olsen 1989.

Study characteristics
Methods	RCT, placebo‐controlled, double‐blind trial Date of study: not stated Setting: not stated
Participants	Randomised: 15 participants, age range 23 ‐ 72 years, 11 male Inclusion criteria Moderate‐severe psoriasis BSA ≥ 10 Exclusion criteria Pregnancy, kidney insufficiency, liver insufficiency Dropouts and withdrawals 3/15 (20%) Disease flare‐up (n = 3)
Interventions	Intervention A. Acitretin (n = 10), orally, 25/50 mg, daily, 8 weeks Control intervention B. Placebo (n = 5), orally, daily, 8 weeks
Outcomes	Assessments at 8 weeks Primary outcomes of the trial Not clearly defined Secondary outcomes of the trial Body surface area Scale Side effects
Notes	Funding by Hoffman‐La Roche Inc Declarations of interest: not stated
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote (p 681): "Patients were assigned to... in a random, double‐blind fashion" Comment: no description of the method used to guarantee random sequence generation
Allocation concealment (selection bias)	Unclear risk	Quote (p 681): "Patients were assigned to... in a random, double‐blind fashion" Comment: no description of the method used to guarantee allocation concealment
Blinding of participants and personnel (performance bias) All outcomes	High risk	Quote (p 681): "Patients were assigned to... in a random, double‐blind fashion" Comment: visible adverse effects of acitretin such as cheilitis were visible
Blinding of outcome assessment (detection bias) All outcomes	High risk	Quote (p 681): "Patients were assigned to... in a random, double‐blind fashion" Comment: visible adverse effects of acitretin such as cheilitis were visible
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	15 included / Number of participants analysed not stated Comment: no description of the methods used to perform the efficacy analyses and to manage the missing data
Selective reporting (reporting bias)	Unclear risk	Comment: no protocol was available. The prespecified outcomes mentioned in the Methods section were reported