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Systematic reviews in context: highlighting systematic reviews relevant to Africa in the Pan African Medical Journal

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      Abstract

      Health research serves to answer questions concerning health and to accumulate facts (evidence) required to guide healthcare policy and practice. However, research designs vary and different types of healthcare questions are best answered by different study designs. For example, qualitative studies are best suited for answering questions about experiences and meaning; cross-sectional studies for questions concerning prevalence; cohort studies for questions regarding incidence and prognosis; and randomised controlled trials for questions on prevention and treatment. In each case, one study would rarely yield sufficient evidence on which to reliably base a healthcare decision. An unbiased and transparent summary of all existing studies on a given question (i.e. a systematic review) tells a better story than any one of the included studies taken separately. A systematic review enables producers and users of research to gauge what a new study has contributed to knowledge by setting the study’s findings in the context of all previous studies investigating the same question. It is therefore inappropriate to initiate a new study without first conducting a systematic review to find out what can be learnt from existing studies. There is nothing new in taking account of earlier studies in either the design or interpretation of new studies. For example, in the 18th century James Lind conducted a clinical trial followed by a systematic review of contemporary treatments for scurvy; which showed fruits to be an effective treatment for the disease. However, surveys of the peer-reviewed literature continue to provide empirical evidence that systematic reviews are seldom used in the design and interpretation of the findings of new studies. Such indifference to systematic reviews as a research function is unethical, unscientific, and uneconomical. Without systematic reviews, limited resources are very likely to be squandered on ill-conceived research and policies. In order to contribute in enhancing the value of research in Africa, the Pan African Medical Journal will start a new regular column that will highlight priority systematic reviews relevant to the continent.

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      The increase in annual global investment in biomedical research--reaching US$240 billion in 2010--has resulted in important health dividends for patients and the public. However, much research does not lead to worthwhile achievements, partly because some studies are done to improve understanding of basic mechanisms that might not have relevance for human health. Additionally, good research ideas often do not yield the anticipated results. As long as the way in which these ideas are prioritised for research is transparent and warranted, these disappointments should not be deemed wasteful; they are simply an inevitable feature of the way science works. However, some sources of waste cannot be justified. In this report, we discuss how avoidable waste can be considered when research priorities are set. We have four recommendations. First, ways to improve the yield from basic research should be investigated. Second, the transparency of processes by which funders prioritise important uncertainties should be increased, making clear how they take account of the needs of potential users of research. Third, investment in additional research should always be preceded by systematic assessment of existing evidence. Fourth, sources of information about research that is in progress should be strengthened and developed and used by researchers. Research funders have primary responsibility for reductions in waste resulting from decisions about what research to do. Copyright © 2014 Elsevier Ltd. All rights reserved.
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        In a retrospective survey, 487 research projects approved by the Central Oxford Research Ethics Committee between 1984 and 1987, were studied for evidence of publication bias. As of May, 1990, 285 of the studies had been analysed by the investigators, and 52% of these had been published. Studies with statistically significant results were more likely to be published than those finding no difference between the study groups (adjusted odds ratio [OR] 2.32; 95% confidence interval [Cl] 1.25-4.28). Studies with significant results were also more likely to lead to a greater number of publications and presentations and to be published in journals with a high citation impact factor. An increased likelihood of publication was also associated with a high rating by the investigator of the importance of the study results, and with increasing sample size. The tendency towards publication bias was greater with observational and laboratory-based experimental studies (OR = 3.79; 95% Cl = 1.47-9.76) than with randomised clinical trials (OR = 0.84; 95% Cl = 0.34-2.09). We have confirmed the presence of publication bias in a cohort of clinical research studies. These findings suggest that conclusions based only on a review of published data should be interpreted cautiously, especially for observational studies. Improved strategies are needed to identify the results of unpublished as well as published studies.
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          Language bias in randomised controlled trials published in English and German.

          Some randomised controlled trials (RCTs) done in German-speaking Europe are published in international English-language journals and others in national German-language journals. We assessed whether authors are more likely to report trials with statistically significant results in English than in German. We studied pairs of RCT reports, matched for first author and time of publication, with one report published in German and the other in English. Pairs were identified from reports round in a manual search of five leading German-language journals and from reports published by the same authors in English found on Medline. Quality of methods and reporting were assessed with two different scales by two investigators who were unaware of authors' identities, affiliations, and other characteristics of trial reports. Main study endpoints were selected by two investigators who were unaware of trial results. Our main outcome was the number of pairs of studies in which the levels of significance (shown by p values) were discordant. 62 eligible pairs of reports were identified but 19 (31%) were excluded because they were duplicate publications. A further three pairs (5%) were excluded because no p values were given. The remaining 40 pairs were analysed. Design characteristics and quality features were similar for reports in both languages. Only 35% of German-language articles, compared with 62% of English-language articles, reported significant (p < 0.05) differences in the main endpoint between study and control groups (p = 0.002 by McNemar's test). Logistic regression showed that the only characteristic that predicted publication in an English-language journal was a significant result. The odds ratio for publication of trials with significant results in English was 3.75 (95% CI 1.25-11.3). Authors were more likely to publish RCTs in an English-language journal if the results were statistically significant. English language bias may, therefore, be introduced in reviews and meta-analyses if they include only trials reported in English. The effort of the Cochrane Collaboration to identify as many controlled trials as possible, through the manual search of many medical journals published in different languages will help to reduce such bias.
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            Author and article information

            Affiliations
            [1 ]Centre for Evidence-based Health Care, Faculty of Medicine and Health Sciences, Stellenbosch University, Cape Town, South Africa
            [2 ]Cochrane South Africa, South African Medical Research Council, Cape Town, South Africa
            [3 ]The Pan African Medical Journal, Center for Public Health Research and Information, Nairobi, Kenya
            Author notes
            [& ]Corresponding author: Charles Shey Wiysonge, Centre for Evidence-based Health Care, Faculty of Medicine and Health Sciences, Stellenbosch University, Cochrane South Africa, South African Medical Research Council, Cape Town, South Africa
            Journal
            Pan Afr Med J
            Pan Afr Med J
            PAMJ
            The Pan African Medical Journal
            The African Field Epidemiology Network
            1937-8688
            30 June 2016
            2016
            : 24
            5072844
            PAMJ-24-180
            10.11604/pamj.2016.24.180.10100
            © Charles Shey Wiysonge et al.

            The Pan African Medical Journal - ISSN 1937-8688. This is an Open Access article distributed under the terms of the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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