Some problems with Cochrane reviews of diet and chronic disease Discussion sections in reports of controlled trials published in general medical journals: islands in search of continents? The Medical Review Article Revisited: Has the Science Improved? The most important tasks for peer reviewers evaluating a randomized controlled trial are not congruent with the tasks most often requested by journal editors Completeness of reporting of trials published in languages other than English: implications for conduct and reporting of systematic reviews Organisation of a proposed Cochrane Diet and Nutrition Field Should journals publish systematic reviews that find no evidence to guide practice? Examples from injury research It will take more than an existing exercise programme to prevent injury The Cochrane Collaboration. Association of journal quality indicators with methodological quality of clinical research articles. The Value of Lesser-Impact-Factor Surgical Journals As a Source of Negative and Inconclusive Outcomes Reporting Randomized controlled trials of aprotinin in cardiac surgery: could clinical equipoise have stopped the bleeding? Evolution of poor reporting and inadequate methods over time in 20 920 randomised controlled trials included in Cochrane reviews: research on research study Improving the completeness and transparency of reports of randomized trials in oral health: the CONSORT statement.
The sum of evidence -based nutrition has to be more than a Cochrane-type meta- analysis of r and omised controlled trials ( RCTs ) . Most of the evidence base in nutrition is observational , especially cohort studies . RCTs of diet change through to disease outcome are uncommon and the change has usually been addition or removal of only a single food component . Trials with whole diets through to disease outcome are rare and dietary changes made by individuals are unlikely to be an exact copy of the prescription . It is hard to even imagine a trial in which half ( r and omised ) of a large group of middle-aged people agree to avoid vegetables for 5 y and be followed up to see who will develop cancer . Most of the USA 's health cl aims , permitted by the Food and Drug Administration , are not supported by RCTs . But where controlled trials of nutritional change and disease outcome have been achieved , they must be review ed very carefully . Two Cochrane review s on diet and cardiovascular disease ( CVD ) , published in the widely read British Medical Journal ( BMJ ) , were criticised after their publication and the conclusions have not been subsequently adopted by expert committees . The first of these review s was ‘ Dietary fat and prevention of CVD : a systematic review ’ . The second was ‘ Systematic review of long term effects of advice to reduce dietary salt in adults ’ . A critique of these two Cochrane review s is presented here as a contribution to our discussion of the potential of Cochrane methodology to the reliability of knowledge about diet and disease CONTEXT Several journals have adopted the Consoli date d St and ards of Reporting Trials ( CONSORT ) recommendations to make assessment of the quality of r and omized controlled trials ( RCTs ) easier . One of these recommendations is that the trial 's results be discussed in light of the totality of the available evidence . OBJECTIVE To assess the extent to which reports of RCTs published in 5 general medical journals have discussed new results in light of all available evidence . DESIGN Assessment of the discussion sections in all 26 reports of RCTs published during May 1997 in Annals of Internal Medicine , BMJ , JAMA , The Lancet , and The New Engl and Journal of Medicine . MAIN OUTCOME MEASURE The inclusion or mention of a systematic review in the discussion section of each article . RESULTS In only 2 articles were the RCT 's results discussed in the context of an up date d systematic review of earlier trials . In a further 4 articles , references were made to relevant systematic review s , but no attempts were made to integrate the results of the new trials in up date d versions of these review s. One article was probably the first published trial to address the question studied . The remaining 19 articles included no evidence that any systematic attempt had been made to set the reported trial 's results in the context of previous trials . CONCLUSION There is little evidence that journals have adequately implemented the CONSORT recommendation that results of an RCT be discussed in light of the totality of the available evidence Review articles are an important element of most medical journals and a popular source of information for clinicians ( 1 ) . Given the increasing volume of medical literature and the limited time for reading that busy clinicians have , reliance on review articles is likely to increase . However , concerns have been raised that narrative , non systematic review articles may produce biased conclusions ( 2 , 3 ) . Mulrow ( 4 ) examined 50 review articles published in four major medical journals ( The New Engl and Journal of Medicine , Annals of Internal Medicine , JAMA , and Archives of Internal Medicine ) in 1985 - 1986 and found that none fulfilled 8 explicit criteria for scientifically sound summaries of the evidence . As a result , she and others ( 5 , 6 ) proposed criteria for conducting and evaluating review articles that would improve their quality ; these criteria are the first 10 listed in the Appendix Table . In a study of 36 review articles done by nine content experts and method ologists , these criteria were shown to yield reliable and valid estimates of the scientific quality of review s ( 7 , 8) . We sought to describe the methods used in recently published review articles and determine whether the attention paid to the method ologic shortcomings of review articles has led to improvements in their scientific quality . Methods By using the Science Citation Index ( 9 ) , we stratified the 12 general medicine journals that are considered core journals for ACP Journal Club ( 10 ) into those with high impact factors ( scores 5 ) and those with lower impact factors . We r and omly selected 3 ( The New Engl and Journal of Medicine , Annals of Internal Medicine , and JAMA ) of the 4 high-impact core journals and 3 ( British Medical Journal , American Journal of Medicine , and Journal of Internal Medicine ) of the 8 core journals with lower impact factors . The sampling frame included 3 of the 4 journals examined in Mulrow 's original study ( 4 ) . All 6 journals were h and - search ed by two of the investigators independently , and review articles published between January and December 1996 were retrieved . Review articles were defined as full-text articles published under the banner review that dealt with disease states ; had the words review , overview , or meta- analysis in the title or abstract ; or indicated in the text that the intention was to review or summarize the literature about a clinical topic . Editorials , correspondence , and conference summaries were excluded . Disagreements on article eligibility ( which occurred in five cases ) were resolved by consensus . After training with a test set of articles , five of the authors used explicit criteria ( Appendix Table ) to rate the identified review articles . So that the raters ' assessment s would be blinded , the articles ' authors , author affiliations , and sources of articles were masked . The first 10 criteria in the Appendix Table ( hereafter referred to as method ologic criteria ) have been previously vali date d ( 7 ) and assess method ologic rigor , whereas the last five criteria were developed for this study to evaluate the scientific basis of treatment recommendations . Because inter-rater agreement was excellent on the test set ( overall agreement , 94 % ) , each rater was assigned a r and om sample of 20 % of the articles . One rater independently evaluated a r and om sample of five articles from each rater to assess inter-rater reliability for the criteria . The mean value was 0.79 , indicating substantial agreement ; overall agreement was 95 % and ranged from 84 % for criteria 1 and 6 to 100 % for criteria 2 , 3 , and 5 . After we determined the number of criteria fulfilled by each article , the number of articles meeting each criterion was ascertained . The proportion of review s from high-impact journals and from lower-impact journals that met each criterion were compared . Only the subset of review s containing treatment recommendations were used for the comparisons for criteria 7 to 15 . The chi-square test was used and 95 % CIs for the observed differences were calculated for all comparisons . In addition , articles identified as meta-analyses , systematic review s , or overviews in their title , abstract , or text were compared with the remaining review articles for each criterion ( again by using the chi-square test and by limiting analysis to those that included treatment recommendations for criteria 7 to 15 ) . Logistic regression analysis was used to adjust for journal of publication . The funding organizations were not involved in the design , conduct , analysis , or reporting of this study . Results A total of 158 review articles were identified : 60 from The New Engl and Journal of Medicine , 33 from Annals of Internal Medicine , 24 from British Medical Journal , 18 from American Journal of Medicine , 13 from JAMA , and 10 from Journal of Internal Medicine . ( A full list of the included articles is available from Dr. McAlister on request . ) Most review s were written by more than one author ( median number of authors , 2 [ range , 1 to 10 authors ] ) , and 111 review s ( 70 % ) made treatment recommendations . Although most articles had sections review ing the relevant pathophysiology and pharmacodynamics , 19 articles ( 12 % ) were largely basic science review s. Only 2 review s met all 10 method ologic criteria ; the median number of criteria fulfilled was one ( Figure ) . Nineteen ( 12 % ) of the review articles were described as meta- analysis , systematic review , or overview in the title or abstract ; 12 of these 19 articles were published in high-impact journals . A higher proportion of these articles met the method ologic criteria ( Appendix Table ) ; the comparisons for all but criterion 6 were statistically significant , even after adjustment for journal of publication ( P<0.005 for all comparisons ) . Although there was significant heterogeneity among journals ( P<0.005 for criteria 1 to 5 , 7 , and 8) , review articles published in high-impact journals did not meet method ologic criteria more frequently than those published in other journals ( Table ) . Exclusion of the review s from one journal with method ologic scores that were significantly lower than the rest ( P<0.001 for all comparisons ) resolved much of the interjournal heterogeneity and revealed that review s published in the remaining high-impact journals more often met some ( but not all ) of the method ologic criteria ( Table ) . Figure . Percentage of 158 review articles published in 1996 that fulfilled specific method ologic criteria . Table . Comparison of Methods Used in 1996 Review Articles , by Journal Impact Factor The 44 articles that described how evidence was located used the following sources ( which were not mutually exclusive ) : MEDLINE ( 42 articles ) , h and search of reference lists from published studies or review articles ( 30 articles ) , other electronic data bases ( 14 articles ) , contact with experts in the field ( 10 articles ) , h and search of relevant journals ( 7 articles ) , and contact with the pharmaceutical industry ( 5 articles ) . Of the 22 review s that included a description of the electronic search strategy , the search was restricted to English- language publications in 11 . Of the 111 review s in which treatment recommendations were made , a median of 3 therapies ( range , 1 to 23 therapies ) were discussed . The 16 meta-analyses that included treatment recommendations were more focused , examining a median of 1 therapy ( range , 1 to 6 therapies ) . The scientific basis of these recommendations is outlined in the last five criteria of the Appendix Table . Discussion In summary , only a minority of the review articles published in six widely read general medical journals specified rigorous , systematic methods of identifying , evaluating , and synthesizing the evidence , thereby raising concerns about the validity of their conclusions and recommendations ( 11 ) . Furthermore , although most review articles made recommendations for therapeutic options , their clinical relevance may be limited : Only one third discussed benefits and harms of the treatment options , only 6 % mentioned the relative or absolute costs of the various options , less than half provided an estimate of the anticipated treatment effect , and very few presented the results in clinical ly relevant formats that would be easily understood by clinicians . Although there is still substantial room for improvement , these results do represent progress from the situation in 1985 - 1986 ( Appendix Table ) . A higher proportion of recently published review s specify how the evidence was identified and synthesized . This same pattern was observed in a recent study of oncology review articles published in a single journal between 1983 and 1995 ( 12 ) . Similarly , our findings for meta-analyses published in these journals in 1996 are consistent with contemporaneous investigations in other fields and represent substantial improvement over the state of affairs in the mid-1980s ( 13 , 14 ) . Our study had several potential limitations . First , the authors of articles in which systematic methods were not specified may have used such methods but not reported them ( or the journal may have removed the details of the methods in prepublication ) . However , preliminary evidence suggests that there is little difference between the conduct of studies and their published methods ( 7 , 15 ) . In other words , if what was done is not reported , there is a good chance that it was not done rigorously ( 7 ) . Second , our finding that meta-analyses are more scientifically rigorous than other review s may be seen as tautological because the criteria used in this study may be used by meta-analysts in performing their studies . However , meta-analysts disagree over some issues of methodology , and published meta-analyses often vary in the quality of their reports ( 13 ) . Third , the practical importance of the method ologic flaws identified in these review s is difficult to ascertain . We lack empirical evidence that review s with explicit , systematic methods yield results closer to the truth , but it is known that non systematic review s are more prone to r and om and Background The peer review process is a cornerstone of biomedical research publications . However , it may fail to allow the publication of high- quality articles . We aim ed to identify and sort , according to their importance , all tasks that are expected from peer review ers when evaluating a manuscript reporting the results of a r and omized controlled trial ( RCT ) and to determine which of these tasks are clearly requested by editors in their recommendations to peer review ers . Methods We identified the tasks expected of peer review ers from 1 ) a systematic review of the published literature and 2 ) recommendations to peer review ers for 171 journals ( i.e. , 10 journals with the highest impact factor for 14 different medical areas and all journals indexed in PubMed that published more than 15 RCTs over 3 months regardless of the medical area ) . Participants who had peer- review ed at least one report of an RCT had to classify the importance of each task relative to other tasks using a Q-sort technique . Finally , we evaluated editors ’ recommendations to authors to determine which tasks were clearly requested by editors in their recommendations to peer review ers . Results The Q-sort survey was completed by 203 participants , 93 ( 46 % ) with clinical expertise , 72 ( 36 % ) with method ological/statistical expertise , 17 ( 8 % ) with expertise in both areas , and 21 ( 10 % ) with other expertise . The task rated most important by participants ( evaluating the risk of bias ) was clearly requested by only 5 % of editors . In contrast , the task most frequently requested by editors ( provide recommendations for publication ) , was rated in the first tertile only by 21 % of all participants . Conclusions The most important tasks for peer review ers were not congruent with the tasks most often requested by journal editors in their guidelines to review ers BACKGROUND Lately , the number of systematic review s published has increased substantially . Many systematic review s exclude trials published in language s other than English . However , there is little empirical evidence to support this action . We looked for differences in the completeness of reporting between trials published in other language s and those published in English , to see whether the exclusion of trials published in other language s is justified . METHODS We compared completeness of reporting , design characteristics , and analytical approaches of 133 r and omised controlled trials ( RCTs ) published in English between 1989 and 1994 and 96 published in French , German , Italian , or Spanish during the same time . RCTs were identified by h and search ing of journals ( seven in English and six in the other language s ) . FINDINGS We found no significant differences between trials published in English and other- language trials for any single item in the completeness of reporting scale ( r and omisation , double-blinding , withdrawals ) , or for the overall score ( percentage of maximum possible score 51.0 % for trials in English , 46.2 % for trials in other language s ; 95 % CI for difference -1.1 to 10.5 ) . Other- language trials were more likely than English- language trials to have adult participants , to use two or more interventions , and to compare two or more active treatments without an untreated control group . Trials in other language s were less likely to report a clearly prespecified primary outcome or any rationale for sample size estimation . INTERPRETATION These results provide evidence for inclusion of all trial reports , irrespective of the language in which they are published , in systematic review s. Their inclusion is likely to increase precision and may reduce systematic errors . We hope that our findings will prove useful to those developing guidelines and policies for the conduct of reporting of systematic review The Cochrane Collaboration helps people make well-informed decisions about health care by preparing , maintaining and promoting the accessibility of systematic review s of the effects of healthcare interventions . In all , 51 Cochrane Review Groups are responsible for preparing and maintaining the review s. Most of these Review Groups are problem-based . However , there are a number of areas or dimensions of health care , such as the setting of care ( eg primary care ) or the type of patient/consumer ( eg older persons ) , that can not be usefully conceptualised as ‘ health problems ’ . In order to reflect the interests of these dimensions , or ‘ fields ’ , of health care more effectively , the Cochrane Collaboration created another type of entity : Cochrane Fields or Networks . The core functions of these Fields are described . It is proposed that a new Cochrane Subfield for Diet and Nutrition should be set up to attract a cadre of new review ers in order to ensure the proper representation of diet and nutrition expertise in the relevant Collaborative Review Groups . The method ological pitfalls of the use of nonr and omised studies will be a key issue for the new Subfield , since the focus of the Cochrane Collaboration 's programme of search ing data bases , journals and conference proceedings has been on the identification of reports of r and omised controlled trials ( RCTs ) . Some of these sources will be need to be search ed again for non- RCT studies . The financial considerations of establishing of a Cochrane Subfield for Diet and Nutrition are discussed Many systematic review s are inconclusive and reinforce the message that there is clinical uncertainty . Phil Alderson and Ian Roberts argue that journals should make a point of publishing such review s rather than waiting for review s that show marked benefit or harm . Some experts disagree , however , but we failed to persuade them to commit their views to print . Studies with dramatic findings make interesting reading . Journal editors underst and ably want to publish articles that their readers will enjoy . This is one cause of publication bias , where research with less dramatic results tends to be published in journals with a smaller circulation , if indeed it is published at all . Systematic review s are no less vulnerable to this bias than other types of research . Should journals resist this pressure and make a point of publishing systematic review s even if all they show is continuing clinical uncertainty ? The answer will depend on the importance we attach to demonstrating uncertainty in medical practice . # # # # Summary points Denying uncertainty does not benefit patients and may increase health service costs More large scale r and omised trials need to be conducted based on the “ uncertainty principle ” Systematic review s with more dramatic results tend In 1983 , Ekstr and et al 1 published the first r and omised controlled trial ( RCT ) of an injury prevention programme for team ball sport . Three decades on from this l and mark study , it is worth reflecting on the progress made and the current ‘ state-of-play ’ in the field of team ball sport injury prevention research . The volume of published research has grown considerably with a recent systematic review of team ball sport injury prevention exercise programmes ( IPEPs ) identifying over 50 published trials.2 The scale , quality and outcomes of recent RCTs are also encouraging with a Swedish trial including over 4500 female soccer players and demonstrating a 64 % reduction  in the rate of anterior cruciate ligament ( ACL ) injuries.3  In 2013 , a subsequent sub analysis of the original Swedish RCT , published in this journal , highlighted the importance of adequate IPEP compliance in preventing injuries . The ACL injury rate was 88 % lower in highly compliant players , compared to those with low compliance.4 A 3-year follow-up,5 also published in this journal , investigated if coaches from the original trial and others in the same target Twenty years ago , you could read all the literature in your field , said reference librarian Kathy Robbins , PhD , MLIS , scanning shelf after shelf of medical journals at the University of Minnesota Bio-Medical Library in Minneapolis . Now , 6000 journal articles are published each day . Merely keeping up with this torrent of information in one 's own specialty is difficult enough . Synthesizing and applying the knowledge to patient care verges on the impossible without some sort of guidance . Fortunately , this guidance is available . Bringing the fruits of new research to the bedside takes at least four levels of review , said Brian Haynes , MD , PhD , professor and chair of the department of clinical epidemiology at McMaster University in Hamilton , Ontario , Canada . Publications such as ACP Journal Club ( of which Haynes is the editor ) collect relevant trials ; the Cochrane Collaboration synthesizes studies of a given research question ; Evidence -Based Medicine Review s integrates the material ; and Clinical Evidence from the British Medical Journal organizes the information according to clinical topic areas , bringing the material closer to practitioners . The goal of the Cochrane Collaboration is to improve the quality of decisions in health care by preparing , maintaining , and promoting the accessibility of systematic review s of the effects of health care interventions . The Cochrane Collaboration has consistently used r and omized , controlled trials ( RCTs ) as the principal focus of its review s. For medical research , The Cochrane Collaboration is a good place to start , said Robbins . If the answer is there , you save time , because the Collaboration has already done the work of search ing journals . The Cochrane Collaboration and Evidence -Based Medicine The Cochrane Collaboration , which is almost a decade old , has a special flavor because its members receive no financial compensation for their contributions . Another noteworthy aspect of the Collaboration is its origin , which stems from the inspiration of one person . Archibald L. Cochrane was a charismatic British epidemiologist whose call for a hard look at how to tell which interventions did more harm than good inspired the formation of a worldwide consortium that prepares systematic review s of r and omized clinical trials . Both evidence -based medicine and the Cochrane Collaboration have roots in the same soil , said Haynes . The origins were n't spontaneous on either side of the Atlantic , said Haynes . Public investment in health care research after World War II had finally produced results that had gone from the laboratory to r and omized , controlled trials . At that point , there was still a gap between evidence and practice . Closing that gap meant knowing which interventions worked and how well . At McMaster , this led to work by Haynes and David Sackett , joined by Alvan Feinstein at Yale , and others , in what was then called critical appraisal of medical literature . ( According to Haynes , the term evidence -based medicine was not introduced until 1991 in an article by Gordon Guyatt in ACP Journal Club . ) In Britain , similar impulses led to the Cochrane Collaboration . Archie Cochrane : A History Kay Dickersin , PhD , codirector of the Collaboration 's New Engl and Center , has written that Archie Cochrane was one of the first to advance the notion that health services must be evaluated on the basis of scientific evidence rather than on clinical impression , anecdotal experience , expert opinion , or tradition .  Cochrane was born in Scotl and in 1909 , graduated from the University of Cambridge , and studied medicine at University Hospital in London . He joined the Royal Army Medical Corps in 1939 and was taken prisoner in 1941 when the German army overran British forces defending the Greek isl and of Crete .  Cochrane spent the rest of the war in prisoner-of-war camps in Greece and Germany , often as the only medical officer serving thous and s of fellow prisoners . Some of the prisoners in the camp in Greece developed edema in their legs , which Cochrane hypothesized was a form of beriberi caused by vitamin B deficiency . He divided his patients into two groups and added yeast to the diet of one group . The intervention worked , and he then persuaded German army officials at the camp to provide yeast to all inmates . It was , Cochrane wrote , his first , worst , and most successful trial ( Cochrane AL . Br Med J [ Clin Res Ed ] . 1984;289:1726 - 7 ) . Later in Germany , when caring for prisoners with tuberculosis , he lamented the lack of hard evidence on whether and when to perform pneumothorax or thoracoplasty . These experiences and observations inspired a postwar career in epidemiology . After the war , Cochrane returned to London and studied statistics under Bradford Hill ( who would publish the first major r and omized clinical trial , on streptomycin to treat pulmonary tuberculosis , in 1948 ) . Cochrane settled in Cardiff , Wales , where over the next 20 years , he studied the epidemiology of tuberculosis and pneumoconiosis . In 1972 , Cochrane published Effectiveness and Efficiency : R and om Reflections on Health Services , in which he argued that r and omized clinical trials could separate valuable interventions from harmful or useless ones . Seven years later , he wrote : It is surely a great criticism of our profession that we have not organized a critical summary , by specialty or subspecialty , adapted periodically , of all relevant r and omized , controlled trials . Cochrane was especially critical of obstetrics and gynecology , which had failed to evaluate properly new innovations in the field ( such as the move to universal hospital delivery for childbirth and the introduction of Papanicolaou smears for cancer screening of the cervix ) before widespread introduction . Iain Chalmers , an obstetrician in Cardiff who knew Cochrane and his work , found Cochrane 's ideas compelling . If one is going to make rational use of limited re sources for health care , one needs to know which of the many things that people are doing within health care have been shown in reliable research studies to be more likely to do good than harm , said Chalmers recently . And the search for and analysis of the evidence needed to provide this information base should be systematic . The First RCT Registry Thus inspired , Chalmers set out in 1974 to create a comprehensive register of all r and omized clinical trials in perinatal medicine ( pregnancy through postpartum day 28 ) . At the time , a MEDLINE search might have retrieved barely half of all trials published after 1965 . Chalmers directed a team of volunteers in h and search ing 50 journals , going as far back as 1940 . They accumulated 3500 trial reports , and their compilation result ed in the publication in 1985 of A Classified Bibliography of Controlled Trials in Perinatal Medicine , 19401984 . Rapid progress in the field , however , meant that the volume was out of date almost immediately after it was printed , said Dickersin . A regularly up date d , electronic version first appeared in 1988a harbinger of later storage and distribution systems ( Dickersin K , Manheimer E. Clin Obstet Gynecol . 1998;41:315 - 31 ) . Further analytic work by Chalmers and others based on this bibliographic material yielded several volumes on perinatal medicine , including a 350-page paperback , Guide to Effective Care in Pregnancy and Childbirth , that presented the conclusions of the full versions in ways immediately useful to women using the maternity services . The systematic review s that were initially published on paper in three books were then kept up to date in a semi-annual electronic publication called The Oxford Data base of Perinatal Trials . Birth of the Cochrane Collaboration In 1993 , Chalmers and an international group of about 70 others jointly announced the formation of the Cochrane Collaboration to prepare , maintain , and disseminate systematic review s of the effects of health care interventions . Dickersin was the principal U.S. representative at the inaugural meeting . The Collaboration 's systematic review s entail exhaustive literature search es and the selection and analysis of studies based on explicit , prespecified criteria , sometimes , but not always , using meta-analyses , which are formal , mathematical combinations of numerical results . With the traditional review article , there are no guidelines about how to do it and no transparency for the reader . You ca n't tell if they 've really plowed through the literature or just picked over their file cabinets , said Dickersin , now associate professor of community health at Brown University School of Medicine in Providence , Rhode Isl and . Meta-analyses , to be good , must be of high quality and appropriate . Sometimes they may lump data together from both r and omized and observational trials or exhibit other biases . When poor meta-analyses are associated with systematic review s , people may assume guilt by association . Clinical practice guidelines may be an outgrowth of systematic review s , but they should be done by different peopleclinicians and professional organizations , she said . How Cochrane Works The Collaboration is made up of review groups , centers , fields , methods groups , and the consumer network . The review groups search for , collect , and analyze RCTs relating to specific health conditions . The 15 centers that constitute the Collaboration are geographically dispersed across 13 countries . In addition to coordinating the review activities within their region , each center also performs specialized functions . The San Francisco Center , for instance , advises on the electronic feedback and peer- review system . An elected 12-member steering group oversees the entire organization , supported by a small secretariat based in Oxford . The real work of the Collaboration takes place in the review groups , building on the model established by Chalmers ' work on perinatal medicine . Initiative for review s generally comes from members who suggest topics to the groups , explained Lisa A. Bero , PhD , associate professor of health policy studies CONTEXT The ability to identify scientific journals that publish high- quality research would help clinicians , scientists , and health-policy analysts to select the most up-to- date medical literature to review . METHODS To assess whether journal characteristics of ( 1 )  peer- review status , ( 2 ) citation rate , ( 3 ) impact factor , ( 4 ) circulation , ( 5 ) manuscript acceptance rate , ( 6 ) MEDLINE indexing , and ( 7 ) Br and on/Hill Library List indexing are predictors of method ological quality of research articles , we conducted a cross-sectional study of 243 original research articles involving human subjects published in general internal medical journals . RESULTS The mean ( SD ) quality score of the 243 articles was 1.37 ( 0.22 ) . All journals reported a peer- review process and were indexed on MEDLINE . In models that controlled for article type ( r and omized controlled trial [ RCT ] or non- RCT ) , journal citation rate was the most statistically significant predictor ( 0.051 increase per doubling ; 95 % confidence interval [ CI ] , 0.037 - 0.065 ; P<.001 ) . In separate analyses by article type , acceptance rate was the strongest predictor for RCT quality ( -0.113 per doubling ; 95 % CI , -0.148 to -0.078 ; P<.001 ) , while journal citation rate was the most predictive factor for non- RCT quality ( 0.051 per doubling ; 95 % CI , 0.044 - 0.059 ; P<.001 ) . CONCLUSIONS High citation rates , impact factors , and circulation rates , and low manuscript acceptance rates and indexing on Br and on/Hill Library List appear to be predictive of higher method ological quality scores for journal articles Objectives : ( 1 ) Examine the tendency of  peer- review ed surgical journals  to publish positive reports or negative and inconclusive outcome articles as a function of the journals ’ impact factor ( IF ) . ( 2 ) Examine the frequency with which surgical journal editors/publishers adhere to the International Committee of Medical Journal Editors statement on sources of funding and /or conflicts of interest ( COI ) . Background : Evidence -based medicine is often used as a template for measuring quality of medical care . Clinicians put their faith in peer- review ed articles as quality -assured and reliable information . However , peer- review ed literature does not provide balanced access to positive , negative , and inconclusive reports . Funding may also influence the decision to publish certain articles and can thus add to the reported bias in the literature . Methods : Articles from 15 surgical journals comprising 3 separate journal groups based upon 2006 impact factor ( IF ) rankings were review ed . All were published in 2007 . Manuscripts were classified by 5 independent review ers as having positive , negative , or inconclusive primary and secondary outcomes and for statements on funding /COI . Positive reports were defined as P < 0.05 , null hypothesis rejected ; negative reports defined as P < 0.05 , null hypothesis accepted ; and inconclusive reports defined as P > 0.05 . Inter-observer consistency was affirmed . Separate analysis of r and omized controlled trials ( RCT ) was performed to assess for the quality of published positive and negative trials . Results : We evaluated 2457 published articles .  Positive primary outcomes were reported in 67 % to 100 % of studied articles in selected journals . Negative and inconclusive primary outcomes were less likely to be reported , except for one journal that reported a high of 33 % negative articles . Higher-ranked journals published fewer negative and inconclusive studies ( 5%–7 % ) than both medium- and lowly-ranked journals ( P < 0.0001 ) . The proportion of RCTs published varied , constituting 18 % to 21 % of articles in the 5 high-ranked journals compared to 6 % to 14 % in the 5 more lowly ranked journals ( P < 0.0001 ) . Reporting of COIs and funding were more frequent in high-IF compared to low-IF journals ( P < 0.0001 ) . Conclusions : Quality rather than outcome should be the measure on which a publication decision is made ; commercial bias may further complicate this balance . Lower IF-rated journals may serve a decidedly useful purpose by publishing more negative and inconclusive outcome studies . The practice of focusing disproportionately on the positive outcomes of most studies may result in unbalanced evidence Background Aprotinin is a serine protease inhibitor used to limit perioperative bleeding and reduce the need for donated blood transfusions during cardiac surgery . R and omized controlled trials of aprotinin evaluating its effect on the outcome of perioperative transfusion have been published since 1987 , and systematic review s were conducted in 1992 and 1997 . Methods A systematic search was conducted for all RCTs of aprotinin  that used placebo controls or were open-label with no active control treatment . Data collected included the primary outcome , objective of each study , whether a systematic review was cited or conducted as part of the background and /or rationale for the study and the number of previously published RCTs cited . Cumulative meta-analyses were performed . Results Sixty-four r and omized , controlled trials of aprotinin were found , conducted between 1987 and 2002 , reporting an endpoint of perioperative transfusion .  Median trial size was 64 subjects , with a range of 20 to 1784 . A cumulative meta- analysis indicated that aprotinin greatly decreased the need for perioperative transfusion , stabilizing at an odds ratio of 0.25 ( p , 10 2 6 ) by the 12th study , published in June of 1992 . The upper limit of the confidence interval never exceeded 0.65 and results were similar in all subgroups . Citation of previous RCTs was extremely low , with a median of 20 % of prior trials cited . Only 7 of 44 ( 15 % ) of subsequent reports referenced the largest trial ( N 1/4 1784 ) , which was 28 times larger than the median trial size . Conclusions This study demonstrates that investigators evaluating aprotinin were not adequately citing previous research , result ing in a large number of RCTs being conducted to address efficacy questions that prior trials had already definitively answered . Institutional review boards and journals could reduce the number of redundant trials by requiring investigators to conduct adequate search es for prior evidence and conducting systematic review Objective To examine how poor reporting and inadequate methods for key method ological features in r and omised controlled trials ( RCTs ) have changed over the past three decades . Design Mapping of trials included in Cochrane review s. Data sources Data from RCTs included in all Cochrane review s published between March 2011 and September 2014 reporting an evaluation of the Cochrane risk of bias items : sequence generation , allocation concealment , blinding , and incomplete outcome data . Data extraction For each RCT , we extracted consensus on risk of bias made by the review authors and identified the primary reference to extract publication year and journal . We matched journal names with Journal Citation Reports to get 2014 impact factors . Main outcomes measures We considered the proportions of trials rated by review authors at unclear and high risk of bias as surrogates for poor reporting and inadequate methods , respectively . Results We analysed 20 920 RCTs ( from 2001 review s ) published in 3136 journals . The proportion of trials with unclear risk of bias was 48.7 % for sequence generation and 57.5 % for allocation concealment ; the proportion of those with high risk of bias was 4.0 % and 7.2 % , respectively . For blinding and incomplete outcome data , 30.6 % and 24.7 % of trials were at unclear risk and 33.1 % and 17.1 % were at high risk , respectively . Higher journal impact factor was associated with a lower proportion of trials at unclear or high risk of bias . The proportion of trials at unclear risk of bias decreased over time , especially for sequence generation , which fell from 69.1 % in 1986 - 1990 to 31.2 % in 2011 - 14 and for allocation concealment ( 70.1 % to 44.6 % ) . After excluding trials at unclear risk of bias , use of inadequate methods also decreased over time : from 14.8 % to 4.6 % for sequence generation and from 32.7 % to 11.6 % for allocation concealment . Conclusions Poor reporting and inadequate methods have decreased over time , especially for sequence generation and allocation concealment . But more could be done , especially in lower impact factor journals PURPOSE R and omized trials provide essential evidence of the effect of interventions in oral health . Such trials need to be appraised by readers in order to decide whether to incorporate new findings into clinical practice and policy in a timely manner . The CONSORT ( Consoli date d St and ards of Reporting of Trials ) Statement is a guidance to facilitate reporting of r and omized controlled trials ( RCTs ) and was first introduced in 1996 . The purpose of this article is to highlight the importance of rigorous reporting of trials in oral health and to discuss the impact of CONSORT on trial reporting . RESULTS Empirical studies demonstrate that key aspects of trial methods influence the size of estimates of studied interventions and bias is a plausible mechanism for some of this effect . Complete and transparent reporting of these methods allows appraisal of the value of trials to be undertaken and the potential for bias to be estimated . Systematic review s have shown that the reported quality of trials in dentistry is poor , thus hindering the underst and ing of the value of individual trials . Since 1996 , CONSORT has been adopted by hundreds of medical journals , international editorial groups , and five dental journals . A systematic review has shown that the quality of reporting of trials improves in journals that have adopted this guidance , although with significant variation , most likely due to differing levels of editorial adherence to it
Adverse gastrointestinal events were more common with high-protein diets .
Multivariable meta-regression analysis showed no significant dose response with higher protein intake .
Conclusions : Higher-protein diets  probably improve adiposity , blood pressure and triglyceride levels , but these effects are small and need to be weighed against the potential for harms
Background / Objectives : Numerous r and omised controlled trials ( RCTs ) published in first tier medical journals have evaluated the health effects of diets high in protein .
We conducted a rigorous systematic review of RCTs comparing higher- and lower-protein diets .