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Research: PITTLER and colleagues, D
Listed in Issue 56
Abstract
PITTLER and colleagues, Department of Complementary Medicine, School of Postgraduate Medicine and Health Sciences, University of Exeter, Exeter, United Kingdom. MHPittler@exeter.ac.uk systematically investigated the location bias in controlled clinical trials of complementary and alternative medicine.
Background
The authors set out to systematically investigate location bias of controlled clinical trials in complementary and alternative medicine (CAM).
Methodology
Literature searches were performed to identify systematic reviews and meta-analyses, which were used to retrieve controlled clinical trials. Trials were categorized by whether they appeared in CAM or mainstream medical (MM) journals, their direction of outcome, methodological quality, and sample size.
Results
351 trials were analysed. A predominance of positive trials was seen in non-impact factor CAM and MM journals, (58) / (78) (74%) and (76) / (102) (75%) respectively, and also in low impact factor CAM and MM journals. In high impact factor MM journals there were equal numbers of positive and negative trials, a distribution significantly different from all other journal categories (P < 0.05). Quality scores were significantly lower for positive than negative trials in non-impact factor CAM journals (P < 0.02). A similar trend was seen in low-impact factor CAM journals, but this was not statistically significant. There were no significant differences between the quality scores of positive and negative trials published in MM journals, except for high impact factor journals, in which positive trials had significantly lower scores than negative trials (P = 0.048). There was no difference between positive and negative trials in any category in terms of sample size.
Conclusion
More positive than negative trials of complementary therapies are published, except in high-impact factor MM journals. In non-impact factor CAM journals positive studies were of poorer methodological quality than the corresponding negative studies. This was not the case in MM journals that published on a wider range of therapies, except in those with high impact factors. Thus location of trials in terms of journal type and impact factor should be taken into account when the literature on complementary therapies is being examined.
References
Pittler MH et al. Location bias in controlled clinical trials of complementary/ alternative therapies. Journal of Clinical Epidemiology 53(5): 485-9. May 2000.
