Bissonnette 2008.

Methods	Placebo‐controlled, parallel‐arm trial Three centres in Canada (community centre clinics) Period of inclusion not stated
Participants	Inclusion criteria Moderate to severe palmoplantar pustulosis (PPPASI score ≥ 8) Age ≥ 18 years Exclusion criteria Pregnancy Immunosuppression Kidney insufficiency Liver insufficiency Washout of 4 weeks for systemic medications and biologics Washout of 2 weeks for PUVA therapy Active infection Uncontrolled cardiovascular condition Uncontrolled diabetes Baseline data: participants were randomised 2:1 to subcutaneous injections of either etanercept 50 mg twice per week (n = 10) or placebo (n = 5) Median age (range), years: 53 (26 to 61) Male/female: 1/9; 0/5 Proportion of participants having psoriatic lesions elsewhere: 8/15 Withdrawal: no dropouts
Interventions	Intervention A: etanercept 50 mg subcutaneously twice per week (10 participants) Control intervention B: placebo (5 participants) Co‐interventions: none Duration of treatment: 3 months
Outcomes	Primary outcome Percentage change in PPPASI scale score Other outcome Adverse events
Notes	The study was funded by Amgen Canada Inc and Wyeth Pharmaceuticals Clinical trial: NCT00353119
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "Subjects were randomised 2:1 to receive subcutaneous injections of either etanercept 50 mg or a placebo" Comment: insufficient information about the sequence generation process to permit judgement
Allocation concealment (selection bias)	Unclear risk	Quote: "Subjects were randomised 2:1 to receive subcutaneous injections of either etanercept 50 mg or a placebo" Comment: the method use to guarantee concealment is not described
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Quote: "double‐blind study" Comment: double‐blind placebo‐controlled. We consider blinding at low risk for trial vs placebo with no obvious clinical adverse events or known specific taste of experimental drug
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote: "double‐blind study" Comment: double‐blind placebo‐controlled. We consider blinding at low risk for trial vs placebo with no obvious clinical adverse events or known specific taste of experimental drug
Incomplete outcome data (attrition bias) All outcomes	Low risk	Quote: "All randomised subjects completed the study" Comment: no missing data (no dropouts neither in the intervention group nor in the control group)
Selective reporting (reporting bias)	Low risk	Comment: the study protocol is available and all of the study’s pre‐specified (primary and secondary) outcomes of interest in the review have been reported in the pre‐specified way