1 Department of Medicine E, Rabin Medical Center, Beilinson Campus, 49100 Petah-Tiqva, Israel; 2 Sackler Faculty of Medicine, Tel-Aviv University, Ramat-Aviv, Tel Aviv, Israel; 3 Journal of Antimicrobial Chemotherapy, 11 The Wharf, 16 Bridge Street, Birmingham B1 2JS, UK
Abstract
Systematic reviews and meta-analyses are powerful tools deployed in the pursuit of evidence-based practice. The Journal of Antimicrobial Chemotherapy (JAC) welcomes the submission of these types of article; however, it is crucial that these studies are conducted properly. In this article we outline the advantages and limitations inherent in these approaches, and the features that we look for when this type of article is submitted to JAC.
Keywords: systematic reviews , meta-analyses , JAC
A systematic review is defined by the Cochrane Handbook as A review of a clearly formulated question that uses systematic and explicit methods to identify, select and critically appraise relevant research, and to collect and analyse data from the studies that are included in the review. Statistical methods (meta-analysis) may or may not be used to analyse and summarize the results of the included studies.1
Most systematic reviews address focussed questions of management and treatment, e.g. which antibiotics should be used to treat leptospirosis? To learn in general about leptospirosis, a narrative review or textbook is probably preferable (Table 1). Usually a systematic review (and a Cochrane review always) will formulate a question before performing the review. The question is composed of the intervention to be addressed, the patient group and the outcome. A clear definition of intervention and patient group helps the authors to decide which studies should be included in the review, but mainly helps the reader to decide whether the results of the systematic review are applicable to their patients.
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Systematic reviews can focus on issues and questions that are important to patients, rather than on single drugs. They can point out areas where evidence is lacking.2 In a systematic review we can choose the outcome that is most important to patients. This is not always the case in primary research. In clinical trials, outcomes are sometimes selected not because of their importance to patients but because a certain choice will reduce the sample size needed or emphasize an alleged advantage of an intervention. Authors of systematic reviews have the privilege (and the duty) to choose the outcomes that really matter to patients. For example, studies on antibiotic or antifungal treatment of severe infections have almost invariably as their primary outcome treatment failure, including modifications of treatment. Given that the patients are alive and well at the end of the infection, it is of minor interest to patients whether the treatment was modified. Systematic reviews, however, selected overall mortality as the primary outcome.3,4
Systematic reviews can examine rare events by accruing events from all original studies. Novel evidence has thus been brought to light by systematic reviews and meta-analysis.4 Single trials are not powered to discover differences in all-cause mortality, adverse events or in induction of resistant strains, while systematic reviews can and should examine such outcomes.5,6
This is why we welcome the submission of systematic reviews. When we publish a systematic review a special section heading is created for it to acknowledge the intense scientific work involved in its compilation and writing, and the important differences from traditional narrative reviews. We will publish Cochrane reviews, and will be careful to point out that they have appeared or will appear in the Cochrane Library as well.
We expect systematic reviews to have sound methods. We expect their authors to combine and present data in a correct manner. But in addition we expect a rich, meaningful synthesis.7 In many systematic reviews the main method to avoid bias is to include only randomized controlled trials. Where evidence from randomized controlled trials is lacking or minimal, we expect authors to inspect the evidence from studies with other designs. The harms related to treatment (adverse effects and induction of resistance) should be surveyed no less systematically than gains. Conclusions of a systematic review should clearly identify the patients for whom these results are relevant and the absolute gain to these patients. In conclusion, we will require of systematic reviews a summation of data and knowledge that goes beyond a mere enumeration of studies and is relevant to patients' care.
Transparency declarations
None to declare.
References
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