Summary of findings 6. Etretinate with PUVA therapy as co‐intervention compared to placebo with PUVA therapy as co‐intervention for chronic palmoplantar pustulosis.

Etretinate with PUVA therapy as co‐intervention compared to placebo with PUVA therapy as co‐intervention for chronic palmoplantar pustulosis
Patient or population: chronic palmoplantar pustulosis Setting: Department of Dermatology Intervention: etretinate with PUVA therapy as co‐intervention Comparison: placebo with PUVA therapy as co‐intervention
Outcomes	Anticipated absolute effects* (95% CI)		Relative effect (95% CI)	No. of participants (studies)	Quality of the evidence (GRADE)	Comments
	Risk with placebo with PUVA therapy as co‐intervention	Risk with etretinate with PUVA therapy as co‐intervention
Proportion of participants cleared or almost cleared in the short term (20 weeks)	Study population		RR 1.91 (1.04 to 3.50)	20 (1 RCT)	⊕⊝⊝⊝ Very lowa	‐
	500 per 1000	955 per 1000 (520 to 1000)
Proportion of participants with adverse effects serious or severe enough to have caused withdrawal ‐ not reported	‐	‐	‐	‐	‐	Not reported
Proportion of participants with at least 50% improvement in their quality of life ‐ not reported	‐	‐	‐	‐	‐	Not reported
Proportion of participants achieving a 50% reduction in disease severity ‐ not reported	‐	‐	‐	‐	‐	Not reported
Proportion of participants without relapse in the long term ‐ not reported	‐	‐	‐	‐	‐	Not reported
Proportion of participants with adverse effects ‐ measured over 20 weeks	There were zero events in the placebo group, so we were unable to calculate the assumed risk. Side effects in the etretinate group: 6 had cheilitis, 4 had hair loss, 2 had peeling of the palmoplantar skin, 1 had generalised peeling of the skin with pruritus, and 1 had dryness of the nasal mucosa.		RR 17.00 (1.11 to 259.87)	20 (1 RCT)	⊕⊝⊝⊝ Very lowa	‐
Ease of compliance to an intervention or a treatment ‐ not reported	‐	‐	‐	‐	‐	Not reported
*The risk in the intervention group (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). CI: confidence interval; PUVA: combination of psoralens and long‐wave ultraviolet radiation; RCT: randomised controlled trial; RR: risk ratio.
GRADE Working Group grades of evidence. High quality: we are very confident that the true effect lies close to that of the estimate of the effect. Moderate quality: we are moderately confident in the effect estimate: the true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different. Low quality: our confidence in the effect estimate is limited: the true effect may be substantially different from the estimate of the effect. Very low quality: we have very little confidence in the effect estimate: the true effect is likely to be substantially different from the estimate of effect.

^aDowngraded by four levels to very low‐quality evidence: two levels for study limitations because the trial was at high risk of bias for blinding and unclear risk for all other items, and a further two levels for imprecision because the result was based on a small trial with few participants and had a large 95% confidence interval.