Chinese medicine formulas for nonalcoholic fatty liver disease: Overview of systematic reviews

BACKGROUND Nonalcoholic fatty liver disease(NAFLD) affects more than one-quarter of the global population. Due to the lack of approved chemical agents, many patients seek treatment from traditional Chinese medicine(TCM) formulas. A variety of systematic reviews have been published regarding the effectiveness and safety of TCM formulas for NAFLD.AIM To critically appraise available systematic reviews and sort out the high-quality evidence on TCM formulas for the management of NAFLD.METHODS Seven databases were systematically searched from their inception to 28 February 2020. The search terms included "non-alcoholic fatty liver disease," "Chinese medicines," "systematic review," and their synonyms. Systematic reviews involving TCM formulas alone or in combination with conventional medications were included. The methodological quality and risk of bias of eligible systematic reviews were evaluated by using A Measure Tool to Assess Systematic Reviews 2(AMSTAR 2) and Risk of Bias in Systematic Review(ROBIS). The quality of outcomes was assessed by the Grading of Recommendations Assessment, Development and Evaluation(GRADE) system.RESULTS Seven systematic reviews were ultimately included. All systematic reviews were conducted based on randomized controlled trials and published in the last decade. According to the AMSTAR 2 tool, one systematic review was judged as having a moderate confidence level, whereas the other studies were rated as having a low or extremely low level of confidence. The ROBIS tool showed that the included systematic reviews all had a high risk of bias due to insufficient consideration of identified concerns. According to the GRADE system, only two outcomes were determined as high quality; namely, TCM formulas with the HuoXueHuaYu principle were better than conventional medications in ultrasound improvement, and TCM formulas were superior to antioxidants in alanine aminotransferase normalization. Other outcomes were downgraded to lower levels, mainly because of heterogeneity among studies, not meeting optimal information sample size, and inclusion of excessive numbers of small sample studies. Nevertheless, the evidence quality of extracted outcomes should be further downgraded when applying to clinical practice due to indirectness.CONCLUSION The quality of available systematic reviews was not satisfactory. Researchers should avoid repeatedly conducting systematic reviews in this area and focus on designing rigorous randomized controlled trials to support TCM formula applications.