Lowe 1991.

Study characteristics
Methods	RCT, placebo‐controlled, double‐blind trial Date of study: not stated Location: 2 centres in Santa Monica and New York City, USA
Participants	Randomised: 34 participants, age range 20 ‐ 75 years, 24 male Inclusion criteria Participants with moderate‐severe psoriasis BSA 20 ‐ 80 ≥ 6 months duration Exclusion criteria Had received conventional systemic treatments or phototherapy for 4 weeks or topical therapy for 2 weeks Dropouts and withdrawals Not specified
Interventions	Intervention A. Acitretin (n = 16), orally, 50 mg, daily, 12 weeks Control intervention B. Placebo (n = 18), orally, daily, 12 weeks Co‐intervention: UVB (phototherapy)
Outcomes	Assessments at 12 weeks Primary outcomes of the trial PASI Secondary outcomes of the trial Side effects
Notes	Funding source (p 591): Quote: "Supported by Roche dermatologics, Nutley, New Jersey and the Skin Research Foundation of California, Santa Monica, California" Declarations of interest; not stated
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote (p 592): "Patients receiving UVB phototherapy were randomly assigned" Comment: no description of the method used to guarantee random sequence generation
Allocation concealment (selection bias)	Unclear risk	Quote (p 592): "Patients receiving UVB phototherapy were randomly assigned" Comment: no description of the method used to guarantee allocation concealment
Blinding of participants and personnel (performance bias) All outcomes	High risk	Quote (p 592): "were randomly assigned to either acitretin or placebo" Comment: no more precision however adverse effects of acitretin such as cheilitis are visible
Blinding of outcome assessment (detection bias) All outcomes	High risk	Quote (p 592): "were randomly assigned to either acitretin or placebo... the same observer who was unaware of patient group examined the patients throughout the investigation" Comment: no more precision but adverse effects of acitretin such as cheilitis are visible
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	34 included / 34 analysed (Table 2) Comment: no description of the method used to manage the missing data or to perform the analyses
Selective reporting (reporting bias)	Unclear risk	Comment: no protocol was available. The prespecified outcomes mentioned in the Methods section appeared to have been reported