Objective: To summarize the current state of evidence for combination topical and systemic therapies for mild to severe psoriasis. Data Sources: We performed a systematic search for all entries in PubMed, CINAHL, Cochrane Review, and EMBASE related to combination treatments for psoriasis through July 2010. Study Selection: We included randomized controlled trials that reported proportion of disease clearance or mean change in clinical severity score (or provided these data through communication with study authors) for efficacy of a combination treatment for psoriasis compared with 1 or more corresponding monotherapies. Data Extraction: Study data were extracted by 3 independent investigators, with disagreement resolved by consensus. The proportion of patients who achieved clearance, definition of clearance, means and standard deviations for baseline disease symptom score and final disease symptom score, and major design characteristics were extracted for each study. Data Synthesis: Combination treatments consisting of vitamin D derivative and corticosteroid, vitamin D derivative and UV-B, vitamin A derivative and psoralen-UV-A, vitamin A derivative and corticosteroid, vitamin A derivative and UV-B, corticosteroid and hydrocolloid occlusion dressings, UV-B and alefacept, and vitamins A and D derivatives were more effective than 1 or more monotherapies using the likelihood of clearance as the outcome. Blinding status and potency of the corticosteroid treatment used were significant sources of heterogeneity between studies. Conclusions: The results demonstrate the need for additional long-term trials with standardized outcome measures to evaluate the efficacy and adverse effects of combination therapies for psoriasis and highlight the possible effects of trial design characteristics on results.
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