Echinacea for prevention of the common cold: an illustrative overview of how information from different systematic reviews is summarised on the internet.

Abstract

Three systematic reviews of echinacea for the prevention of colds have somewhat different conclusions. Our study objectives were to illustrate how selection criteria for trials in each of the reviews could lead to different conclusions, and to classify the ways in which webpage authors use the reviews to construct advice about echinacea. A funnel plot was constructed of all treatment comparisons in the primary trials included in the reviews. A World Wide Web search was undertaken using five major search engines in order to locate webpages that referred to the efficacy of echinacea in cold prevention and also referred to each of the reviews. Twelve webpages were located. Three webpages presented findings from all three reviews; five presented findings from one or two; four used all three reviews as general supporting references. Views about efficacy differed. There were few comments about the sources of heterogeneity between reviews. Given the residual uncertainty and the gaps between the evidence and the ways that this is summarised on webpages, it may prove difficult for consumers to assimilate the evidence. As well as undertaking high-quality trials in complementary medicine, we also need to ensure precision in the reporting of uncertainty.