The benefits of steroids versus steroids plus antivirals for treatment of Bell's palsy: a meta-analysis
Even when individual studies included in best evidence summaries have a low risk of bias, publication bias can result in substantial overestimates of effect. Authors should suspect publication bias when available evidence comes from a number of small studies, most of which have been commercially funded. A number of approaches based on examination of the pattern of data are available to help assess publication bias. The most popular of these is the funnel plot; all, however, have substantial limitations. The likelihood of publication bias is less for studies that are not evaluating new drugs or devices.