Sommerburg 1993

Methods	RCT, placebo‐controlled, double blind Date of study: 1986‐1988 Location: 7 centres in Germany
Participants	Randomised: 88 participants (mean age 45 years, 68 male) Inclusion criteria Generalized chronic plaque psoriasis or exanthematic Aged 19‐75 years Exclusion criteria Pregnancy, kidney insufficiency, liver insufficiency Had uncontrolled cardiovascular disorder Had uncontrolled diabetes Had uncontrolled hypertension Dropouts and withdrawals 5/88 (6%) Acitretin (4), placebo (1) Missing outcome (3) erythroderma (1)
Interventions	Intervention A. Acitretin (n = 44), orally, 50 mg (15 days) then 25 mg, daily, 8 weeks Control intervention B. Placebo (n = 44), orally, daily, 8 weeks Co‐intervention PUVA (8‐methoxypsoralen), orally 0.6 mg/kg, 3‐5/week, 8 weeks
Outcomes	Assessments at 8 weeks Primary outcomes of the trial PSI Secondary outcomes of the trial PSI 75
Notes	Funding source: not stated Declarations of interest: not stated
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote (p 310): "The study was designed as a randomised, double‐blind, parallel groups trial... Both investigators and biostatisticians were blinded" Comment: no description of the method used to guarantee random sequence generation
Allocation concealment (selection bias)	Unclear risk	Quote (p 310): "The study was designed as a randomised, double‐blind, parallel groups trial... Both investigators and biostatisticians were blinded" Comment: no description of the method used to guarantee allocation concealment
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Quote (p 310 & 311): "The study was designed as a randomised, double‐blind, parallel group trial... Both investigators and biostatisticians were blinded… however due to well know side effect pattern of acitretin, ..., the possibility of an investigator bias cannot be excluded" Comment: visible AE in acitretin groups
Blinding of outcome assessment (detection bias) All outcomes	High risk	Quote (p 310 & 311): " The study was designed as a randomised, double‐blind, parallel group trial... Both investigators and biostatisticians were blinded… however due to well know side effect pattern of acitretin, ..., the possibility of an investigator bias cannot be excluded" Comment: visible AE in acitretin groups
Incomplete outcome data (attrition bias) All outcomes	Low risk	88 included/83 analysed Quote (p 311): "Patients who discontinued the trial prematurely were evaluated on the date of discontinuation of therapy" Comment: not ITT, low number of dropouts
Selective reporting (reporting bias)	Unclear risk	Comment: no protocol was available. The pre‐specified outcomes mentioned in the methods section appeared to have been reported.