Publication and outcome reporting of homeopathy trials registered in ClinicalTrials.gov

Abstract

Background Homeopathy is gaining popularity globally, despite a lack of convincing evidence of its efficacy. For example, a 2015 review by the Australian National Health and Medical Research Council (NHMRC) found no discernible convincing effects beyond placebo. However, a concern was that publication bias and outcome reporting bias could have influenced the results of the included systematic reviews. Objectives To study (i) the rates of non‐publication and (ii) rates and types of alteration of planned outcomes of homeopathy studies registered in ClinicalTrials.gov. Methods We searched ClinicalTrials.gov for all homeopathy trials completed more than 2 years ago. We then checked the trial's publication status by examining the publication field in ClinicalTrials.gov, searching PubMed and finally Google Scholar. We also checked whether the registered primary outcome matched the published primary outcome. Results We found 35 registered homeopathy trials, from 11 countries, completed at least 2 years ago. Of these 35, we found 16 (46%) publications in MEDLINE and Google Scholar. In four (of 16), the primary outcome measures had been switched or modified. Conclusions Of all homeopathy trials registered in ClinicalTrials.gov, only 46% appear to have published within 2 years of completion, of which a quarter altered their primary endpoint. Further research is warranted on the nature and reasons for non‐publication.

Assessing the magnitude of reporting bias in trials of homeopathy: a cross-sectional study and meta-analysis

“…To the best of our knowledge, Thomas et al were the first who assessed the extent of non-publication of trials in the homeopathic literature 23. Their assessment covered the trial literature from 2002 to 2014 and was less comprehensive than ours.…”

“…Overall, however, they reported similar findings as ours. In their sample, 46% of registered trials remained unpublished and in 25% of published homeopathy trials, the primary outcome measures had been switched or modified 23. The consistency of these results indicates that over almost a decade, the situation has not substantially improved…”

“…In their sample, 46% of registered trials remained unpublished and in 25% of published homeopathy trials, the primary outcome measures had been switched or modified. 23 The consistency of these results indicates that over almost a decade, the situation has not substantially improved Consequently, reporting biases are likely to have a substantial impact on the estimated treatment effect of homeopathy. Using data from a highly cited meta-analysis of homeopathy RCTs, our example showed that unregistered trials yielded substantially larger treatment effects than registered trials.…”

“…An assessment by Thomas et al reported that up to the year 2013, only 46% of registered homeopathic trials (16/35) were published. 23 When no information is publicly available about the majority of homeopathic trials, sound conclusions about the efficacy and the risks of using homeopathic medicinal products for treating health conditions are impossible. 24 25 To conduct a comprehensive assessment of the state of registration and publication of trials on homeopathy, our study had four objectives: (1) to determine the proportion of registered trials assessing homeopathy that remains unpublished, (2) to examine whether registered primary outcomes are consistent with published primary outcomes, (3) to assess the proportion of published randomised controlled trials (RCTs) on homeopathy that have been registered in a public clinical trial registry and (4) to gauge the impact of reporting bias on evidence syntheses of homeopathy trials.…”

“…Because regulatory agencies do not require proof of effectiveness for homeopathic products, little attention has been paid to the non-publication of homeopathy trials and its consequences. An assessment by Thomas et al reported that up to the year 2013, only 46% of registered homeopathic trials (16/35) were published 23. When no information is publicly available about the majority of homeopathic trials, sound conclusions about the efficacy and the risks of using homeopathic medicinal products for treating health conditions are impossible 24 25…”