Chinese herbal medicine bath therapy for psoriasis vulgaris using topical calcipotriol as the comparator: A systematic review with meta-analysis and association rule analysis.

ETHNOPHARMACOLOGICAL RELEVANCE: Psoriasis is a chronic inflammatory skin disease. Vitamin D analogues are the first-line topical agents for the long-term management of psoriasis. Chinese herbal medicine (CHM) bath therapy is commonly employed for psoriasis. However, the effects and safety of CHM bath therapy for psoriasis vulgaris, using topical calcipotriol as the comparator, remain inconclusive. Furthermore, the combination of herbs, a distinctive feature of CHM, is essential for its therapeutic effects due to the individual and synergistic properties of the herbs involved.

AIM OF THE STUDY: The review was conducted to evaluate the effectiveness and safety of CHM bath therapy for psoriasis vulgaris, using calcipotriol as the comparator. Potential herbs and herb combinations of CHM bath therapy were also explored for further drug discovery.

MATERIALS AND METHODS: Nine databases were searched from inception until March 05, 2024. Randomised controlled trials (RCTs) investigating CHM bath therapy, using calcipotriol as the comparator, were included. Statistical analyses were performed using RevMan 5.4, Stata 12.0 and SPSS Clementine 12.0 software. The evidence certainty for outcomes was assessed using the approach proposed by the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) Working Group. Moreover, association rule analysis on herbs identified in the systematic review was conducted to explore the potential herbs and herb combinations.

RESULTS: A total of 17 RCTs involving 1,379 participants were included in this systematic review. The findings of this review revealed that: 1) CHM bath therapy produced comparable effects to calcipotriol in reducing Psoriasis Area and Severity Index (PASI), Psoriasis Scalp Severity Index (PSSI), and itch visual analogue scale (VAS) at the end of the treatment phase; as well as exhibited a superior long-term effect than calcipotriol through decreasing relapse rates at the end of the follow-up phase; 2) CHM bath therapy showed an additional benefit when combined with calcipotriol in managing psoriasis vulgaris at the end of the treatment phase, in terms of PASI, PSSI, itch VAS, IL-17, IL-23, CD3+ and CD4+ T cells. The certainty of the evidence was rated as 'very low', 'low' or 'moderate' based on the GRADE assessment, considering some concerns or high risk of bias of included studies, substantial heterogeneity, and existing publication bias of some outcomes. Additionally, the proportions of participants reporting adverse events were similar in both groups. Association rule analysis of all included herbs identified 23 herb combinations including Prunus persica (L.) Batsch and Carthamus tinctorius L., as well as 11 frequently used herbs, such as Kochia scoparia (L.) Schrad., Dictamnus dasycarpus Turcz. And Sophora flavescens Ait.

CONCLUSIONS: The effects of CHM bath therapy were comparable with those of topical calcipotriol but demonstrated a longer-lasting effect. Combining CHM bath therapy with calcipotriol also provided an additional benefit for adult psoriasis vulgaris. However, the certainty of the evidence was downgraded due to the methodological limitations of included studies. To confirm the findings of this review, future investigations should involve double-blinded, placebo-controlled RCTs. Importantly, it appears worthwhile to consider further research for drug development utilising the identified herbs or herb combinations.