Quality and risk of bias in Panax ginseng randomized controlled trials: a review

Panax ginseng is one of the most frequently used herbs in the world. Numerous trials have evaluated its clinical benefits. However, the quality of these studies has not been comprehensively and systematically assessed. We reviewed randomized controlled trials (RCTs) of Panax ginseng to evaluate their quality and risk of bias. We searched four English databases, without publication date restriction. Two reviewers extracted details about the studies' methodological quality, guided by the Consolidated Standards of Reporting Trials (CONSORT) checklist and its extension for herbal interventions. Risk of bias was determined using the Cochrane Risk of Bias tool. Of 475 potentially relevant studies, 58 met our inclusion criteria. In these 58 studies, 48.3% of the suggested CONSORT checklist items and 35.9% of the extended herbal items were reported. The quality of RCTs published after the CONSORT checklist improved. Until 1995 (before CONSORT) (n = 4), 32.8% of the items were reported in studies. From 1996-2006 (CONSORT published and revised) (n = 30), 46.1% were reported, and from 2007 (n = 24), 53.5% were reported (p = 0.005). After the CONSORT extension for herbal interventions was published in 2006, RCT quality also improved, although not significantly. Until 2005 (n = 34), 35.2% of the extended herbal items were reported in studies; and from 2006 onwards (n = 24), 37.3% were reported (p = 0.64). Most studies classified risk of bias as "unclear". Overall, the quality of Panax ginseng RCT methodology has improved since the CONSORT checklist was introduced. However, more can be done to improve the methodological quality of, and reporting in, RCTs.