Impact of searching clinical trial registries in systematic reviews of pharmaceutical treatments: methodological systematic review and reanalysis of meta-analysesBMJ 2017; 356 doi: https://doi.org/10.1136/bmj.j448 (Published 17 February 2017) Cite this as: BMJ 2017;356:j448
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We read with great interest the article "Impact of searching clinical trial registries in systematic reviews of pharmaceutical treatments: methodological systematic review and reanalysis of meta-analyses" by Baudard M. et al1. It analysed the impact of a search strategy including clinical trial registries on the results of published systematic reviews of pharmacological treatments.
The authors reported that 52% of the selected systematic reviews did not report a search of trial registries. Throughout the consultation of the World Health Organization International Trials Registry Platform (WHO ICTRP) search portal, they found 122 additional randomised clinical trials (RCT). Finally, 14 systematic reviews were reanalysed, including 45 RCTs from registries. The addition of data allowed for increasing the number of patients but none of the changes in the summary effect estimates had a qualitative impact in the interpretations of the results. However, the conclusion of the authors was: “Searching clinical trial registries is essential for identifying additional trials that could increase the value of systematic reviews”.
This conclusion seems to be in contrast with the results of the paper.
We need to consider that the aim of a systematic review is providing evidences of efficacy to support clinical decisions. The value of a systematic review should be measured in relation to the capability of detecting the appropriate clinical behaviour. In fact, the methodology of guidelines development2, as the best tool for clinical appropriateness, puts systematic reviews at the highest level in the hierarchy of evidence.
Therefore, considering that the new research strategy reported by Baudard M et al1, did not affect the qualitative results of the systematic review, it is safe to conclude that this research method did not add value to the clinical results and had no implications for clinical practice.
In our opinion, an exhaustive literature search in systematic reviews could be acceptable if it has an impact on clinical outcomes. Sagliocca L. et al3 compared the traditional systematic reviews research method with a more pragmatic approach based on the review of a selected number of core journals. The authors demonstrated, in a sample of systematic reviews, that reproduction of the literature search restricted to major medical journals in the fields, as well as to the most relevant generalist journals, does not alter the quantitative estimates of efficacy, nor the clinical indications.
Finally, we strongly believe that systematic reviews and guidelines are the most valid instrument in supporting clinical decisions and should be conducted according to an accurate and reliable method. The comprehensiveness of a literature search is the main factor influencing the accuracy but should be assessed considering the implications for clinical practice.
1. Baudard M, Yavchitz A, Ravaud P, et al. Impact of searching clinical trial registries in systematic reviews of pharmaceutical treatments: methodological systematic review and reanalysis of meta-analyses. BMJ 2017;356:j448
2. Developing NICE guidelines: the manual. October 2014
3. Sagliocca L, De Masi S, Ferrigno L, et al. A pragmatic strategy for the review of clinical evidence. J Eval Clin Pract. 2013 Aug;19(4):689-96
Competing interests: No competing interests