CONSORT 2010 Statement: updated guidelines for reporting parallel group randomised trials

The CONSORT statement is used worldwide to improve the reporting of randomised controlled trials. Kenneth Schulz and colleagues describe the latest version, CONSORT 2010, which updates the reporting guideline based on new methodological evidence and accumulating experience. To encourage dissemination of the CONSORT

# Introduction
Randomised controlled trials, when appropriately designed, conducted, and reported, represent the gold standard in evaluating healthcare interventions. However, randomised trials can yield biased results if they lack methodological rigour [bib_ref] Systematic reviews in health care: assessing the quality of controlled clinical trials, Juni [/bib_ref]. To assess a trial accurately, readers of a published report need complete, clear, and transparent information on its methodology and findings. Unfortunately, attempted assessments frequently fail because authors of many trial reports neglect to provide lucid and complete descriptions of that critical information [bib_ref] Epidemiology and reporting of randomised trials published in PubMed journals, Chan [/bib_ref] [bib_ref] What is missing from descriptions of treatment in trials and reviews, Glasziou [/bib_ref] [bib_ref] Systematic review of the empirical evidence of study publication bias and outcome..., Dwan [/bib_ref].
That lack of adequate reporting fuelled the development of the original CONSORT (Consolidated Standards of Reporting Trials) statement in 1996 [bib_ref] Improving the quality of reporting of randomized controlled trials. The CONSORT statement, Begg [/bib_ref] and its revision five years later [bib_ref] The CONSORT statement: revised recommendations for improving the quality of reports of..., Moher [/bib_ref] [bib_ref] The CONSORT statement: revised recommendations for improving the quality of reports of..., Moher [/bib_ref] [bib_ref] The CONSORT statement: revised recommendations for improving the quality of reports of..., Moher [/bib_ref]. While those statements improved the reporting quality for some randomised controlled trials, [bib_ref] Does the CONSORT checklist improve the quality of reports of randomised controlled..., Plint [/bib_ref] many trial reports still remain inadequate [bib_ref] Epidemiology and reporting of randomised trials published in PubMed journals, Chan [/bib_ref]. Furthermore, new methodological evidence and additional experience has accumulated since the last revision in 2001. Consequently, we organised a CONSORT Group meeting to update the 2001 statement [bib_ref] The CONSORT statement: revised recommendations for improving the quality of reports of..., Moher [/bib_ref] [bib_ref] The CONSORT statement: revised recommendations for improving the quality of reports of..., Moher [/bib_ref] [bib_ref] The CONSORT statement: revised recommendations for improving the quality of reports of..., Moher [/bib_ref]. We introduce here the result of that process, CONSORT 2010.

## Intent of consort 2010
The CONSORT 2010 Statement is this paper including the 25 item checklist in the table [fig_ref] Table 1: CONSORT 2010 checklist of information to include when reporting a randomised trial* [/fig_ref] and the flow diagram . It provides guidance for reporting all randomised controlled trials, but focuses on the most common design type-individually randomised, two group, parallel trials. Other trial designs, such as cluster randomised trials and non-inferiority trials, require varying amounts of additional information. CONSORT extensions for these designs, [bib_ref] CONSORT statement: extension to cluster randomised trials, Campbell [/bib_ref] [bib_ref] Reporting of noninferiority and equivalence randomized trials: an extension of the CONSORT..., Piaggio [/bib_ref] and other CON-SORT products, can be found through the CONSORT website http://www.consort-statement.org. Along with the CONSORT statement, we have updated the explanation and elaboration article,which explains the inclusion of each checklist item, provides methodological background, and gives published examples of transparent reporting.
Diligent adherence by authors to the checklist items facilitates clarity, completeness, and transparency of reporting. Explicit descriptions, not ambiguity or omission, best serve the interests of all readers. Note that the CONSORT 2010 Statement does not include recommendations for designing, conducting, and analysing trials. It solely addresses the reporting of what was done and what was found.
Nevertheless, CONSORT does indirectly affect design and conduct. Transparent reporting reveals deficiencies in research if they exist. Thus, investigators who conduct inadequate trials, but who must transparently report, should not be able to pass through the publication process without revelation of their trial's inadequacies. That emerging reality should provide impetus to improved trial design and conduct in the future, a secondary indirect goal of our work. Moreover, CON-SORT can help researchers in designing their trial.

# Background to consort
Efforts to improve the reporting of randomised controlled trials accelerated in the mid-1990s, spurred partly by methodological research. Researchers had shown for many years that authors reported such trials poorly, and empirical evidence began to accumulate that some poorly conducted or poorly reported aspects of trials were associated with bias [bib_ref] Empirical evidence of bias. Dimensions of methodological quality associated with estimates of..., Schulz [/bib_ref]. Two initiatives aimed at developing reporting guidelines culminated in one of us (DM) and Drummond Rennie organising the first CONSORT statement in 1996 [bib_ref] Improving the quality of reporting of randomized controlled trials. The CONSORT statement, Begg [/bib_ref]. Further methodological research on similar topics reinforced earlier findings [bib_ref] Does quality of reports of randomised trials affect estimates of intervention efficacy..., Moher [/bib_ref] and fed into the revision of 2001 [bib_ref] The CONSORT statement: revised recommendations for improving the quality of reports of..., Moher [/bib_ref] [bib_ref] The CONSORT statement: revised recommendations for improving the quality of reports of..., Moher [/bib_ref] [bib_ref] The CONSORT statement: revised recommendations for improving the quality of reports of..., Moher [/bib_ref]. Subsequently, the expanding body of methodological research informed the refinement of CONSORT 2010. More than 700 studies comprise the CONSORT database (located on the CONSORT website), which provides the empirical evidence to underpin the CONSORT initiative.
Indeed, CONSORT Group members continually monitor the literature. Information gleaned from these efforts provides an evidence base on which to update the CONSORT statement. We add, drop, or modify items based on that evidence and the recommendations of the CONSORT Group, an international and eclectic group of clinical trialists, statisticians, epidemiologists, and biomedical editors. The CONSORT Executive (KFS, DGA, DM) strives for a balance of established and emerging researchers. The membership of the group is dynamic. As our work expands in response to emerging projects and needed expertise, we invite new members to contribute. As such, CONSORT continually assimilates new ideas and perspectives. That process informs the continually evolving CONSORT statement.
Over time, CONSORT has garnered much support. More than 400 journals, published around the world and in many languages, have explicitly supported the CONSORT statement. Many other healthcare journals support it without our knowledge. Moreover, thousands more have implicitly supported it with the endorsement of the CONSORT statement by the International Committee of Medical Journal Editors http://www.icmje.org. Other prominent editorial groups, the Council of Science Editors and the World Association of Medical Editors, officially support CONSORT. That support Flow diagram of the progress through the phases of a parallel randomised trial of two groups (that is, enrolment, intervention allocation, follow-up, and data analysis). seems warranted: when used by authors and journals, CONSORT seems to improve reporting [bib_ref] Does the CONSORT checklist improve the quality of reports of randomised controlled..., Plint [/bib_ref].

## Development of consort 2010
Thirty one members of the CONSORT 2010 Group met in Montebello, Canada, in January 2007 to update the 2001 CONSORT statement. In addition to the accumulating evidence relating to existing checklist items, several new issues had come to prominence since 2001. Some participants were given primary responsibility for aggregating and synthesising the relevant evidence on a particular checklist item of interest. Based on that evidence, the group deliberated the value of each item. As in prior CONSORT versions, we kept only those items deemed absolutely fundamental to reporting a randomised controlled trial. Moreover, an item may be fundamental to a trial but not included, such as approval by an institutional ethical review board, because funding bodies strictly enforce ethical review and medical journals usually address reporting ethical review in their instructions for authors. Other items may seem desirable, such as reporting on whether on-site monitoring was done, but a lack of empirical evidence or any consensus on their value cautions against inclusion at this point. The CONSORT 2010 Statement thus addresses the minimum criteria, although that should not deter authors from including other information if they consider it important.
After the meeting, the CONSORT Executive convened teleconferences and meetings to revise the checklist. After seven major iterations, a revised checklist was distributed to the larger group for feedback. With that feedback, the executive met twice in person to consider all the comments and to produce a penultimate version. That served as the basis for writing the first draft of this paper, which was then distributed to the group for feedback. After consideration of their comments, the executive finalised the statement.
The CONSORT Executive then drafted an updated explanation and elaboration manuscript, with assistance from other members of the larger group. The substance of the 2007 CONSORT meeting provided the material for the update. The updated explanation and elaboration manuscript was distributed to the entire group for additions, deletions, and changes. That final iterative process converged to the CONSORT 2010 Explanation and Elaboration.

## Changes in consort 2010
The revision process resulted in evolutionary, not revolutionary, changes to the checklist [fig_ref] Table 1: CONSORT 2010 checklist of information to include when reporting a randomised trial* [/fig_ref] , and the flow diagram was not modified except for one word . Moreover, because other reporting guidelines augmenting the checklist refer to item numbers, we kept the existing items under their previous item numbers except for some renumbering of items 2 to 5. We added additional items either as a sub-item under an existing item, an entirely new item number at the end of the checklist, or (with item 3) an interjected item into a renumbered segment. We have summarised the noteworthy general changes in Appendix 1 and specific changes in Appendix 2. The CONSORT website contains a side by side comparison of the 2001 and 2010 versions.

# Implications and limitations
We developed CONSORT 2010 to assist authors in writing reports of randomised controlled trials, editors and peer reviewers in reviewing manuscripts for publication, and readers in critically appraising published articles. The CONSORT 2010 Explanation and Elaboration provides elucidation and context to the checklist items. We strongly recommend using the explanation and elaboration in conjunction with the checklist to foster complete, clear, and transparent reporting and aid appraisal of published trial reports.
CONSORT 2010 focuses predominantly on the two group, parallel randomised controlled trial, which accounts for over half of trials in the literature [bib_ref] Epidemiology and reporting of randomised trials published in PubMed journals, Chan [/bib_ref]. Most of the items from the CONSORT 2010 Statement, however, pertain to all types of randomised trials. Nevertheless, some types of trials or trial situations dictate the need for additional information in the trial report. When in doubt, authors, editors, and readers should consult the CONSORT website for any CONSORT extensions, expansions (amplifications), implementations, or other guidance that may be relevant.
The evidence based approach we have used for CON-SORT also served as a model for development of other reporting guidelines, such as for reporting systematic reviews and meta-analyses of studies evaluating interventions [bib_ref] Preferred reporting items for systematic reviews and meta-analyses: the PRISMA statement, Moher [/bib_ref] , diagnostic studies [bib_ref] Standards for Reporting of Diagnostic Accuracy: Towards complete and accurate reporting of..., Bossuyt [/bib_ref] , and observational studies [bib_ref] Strengthening the reporting of observational studies in epidemiology (STROBE) statement: guidelines for..., Von Elm [/bib_ref]. The explicit goal of all these initiatives is to improve reporting. The Enhancing the Quality and Transparency of Health Research (EQUATOR) Network will facilitate development of reporting guidelines and help disseminate the guidelines: http://www.equatornetwork.org provides information on all reporting guidelines in health research.
With CONSORT 2010, we again intentionally declined to produce a rigid structure for the reporting of randomised trials. Indeed, SORTtried a rigid format, and it failed in a pilot run with an editor and authors [bib_ref] Reporting randomized controlled trials. An experiment and a call for responses from..., Rennie [/bib_ref]. Consequently, the format of articles should abide by journal style, editorial directions, the traditions of the research field addressed, and, where possible, author preferences. We do not wish to standardise the structure of reporting. Authors should simply address checklist Mechanism used to implement the random allocation sequence (such as sequentially numbered containers), describing any steps taken to conceal the sequence until interventions were assigned Implementation 10 Who generated the random allocation sequence, who enrolled participants, and who assigned participants to interventions Blinding 11a If done, who was blinded after assignment to interventions (for example, participants, care providers, those assessing outcomes) and how 11b If relevant, description of the similarity of interventions Statistical methods 12a Statistical methods used to compare groups for primary and secondary outcomes 12b Methods for additional analyses, such as subgroup analyses and adjusted analyses

# Results

## Participant flow (a diagram is strongly recommended)
13a For each group, the numbers of participants who were randomly assigned, received intended treatment, and were analysed for the primary outcome items somewhere in the article, with ample detail and lucidity. That stated, we think that manuscripts benefit from frequent subheadings within the major sections, especially the methods and results sections. CONSORT urges completeness, clarity, and transparency of reporting, which simply reflects the actual trial design and conduct. However, as a potential drawback, a reporting guideline might encourage some authors to report fictitiously the information suggested by the guidance rather than what was actually done. Authors, peer reviewers, and editors should vigilantly guard against that potential drawback and refer, for example, to trial protocols, to information on trial registers, and to regulatory agency websites. Moreover, the CONSORT 2010 Statement does not include recommendations for designing and conducting randomised trials. The items should elicit clear pronouncements of how and what the authors did, but do not contain any judgments on how and what the authors should have done. Thus, CON-SORT 2010 is not intended as an instrument to evaluate the quality of a trial. Nor is it appropriate to use the checklist to construct a "quality score."
Nevertheless, we suggest that researchers begin trials with their end publication in mind. Poor reporting allows authors, intentionally or inadvertently, to escape scrutiny of any weak aspects of their trials. However, with wide adoption of CONSORT by journals and editorial groups, most authors should have to report transparently all important aspects of their trial. The ensuing scrutiny rewards well conducted trials and penalises poorly conducted trials. Thus, investigators should understand the CONSORT 2010 reporting guidelines before starting a trial as a further incentive to design and conduct their trials according to rigorous standards.
CONSORT 2010 supplants the prior version published in 2001. Any support for the earlier version accumulated from journals or editorial groups will automatically extend to this newer version, unless specifically requested otherwise. Journals that do not currently support CONSORT may do so by registering on the CON-SORT website. If a journal supports or endorses CONSORT 2010, it should cite one of the original versions of CONSORT 2010, the CONSORT 2010 Explanation and Elaboration, and the CONSORT website in their "Instructions to authors." We suggest that authors who wish to cite CONSORT should cite this or another of the original journal versions of CONSORT 2010 Statement, and, if appropriate, the CONSORT 2010 Explanation and Elaboration. All CONSORT material can be accessed through the original publishing journals or the CONSORT website. Groups or individuals who desire to translate the CONSORT 2010 Statement into other languages should first consult the CONSORT policy statement on the website.
We emphasise that CONSORT 2010 represents an evolving guideline. It requires perpetual reappraisal and, if necessary, modifications. In the future we will further revise the CONSORT material considering comments, criticisms, experiences, and accumulating new evidence. We invite readers to submit recommendations via the CONSORT website.

## Appendix 1: noteworthy general changes in consort 2010 statement
- We simplified and clarified the wording, such as in items - We improved consistency of style across the items by removing the imperative verbs that were in the 2001 version
- We enhanced specificity of appraisal by breaking some items into sub-items. Many journals expect authors to complete a CONSORT checklist indicating where in the manuscript the items have been addressed. Experience with the checklist noted pragmatic difficulties when an item comprised multiple elements. For example, item 4 addresses eligibility of participants and the settings and locations of data collection. With the 2001 version, an author could provide a page number for that item on the checklist, but might have reported only eligibility in the paper, for example, and not reported the settings and locations. CONSORT 2010 relieves obfuscations and forces authors to provide page numbers in the checklist for both eligibility and settings. Sources of funding and other support (such as supply of drugs), role of funders *We strongly recommend reading this statement in conjunction with the CONSORT 2010 Explanation and Elaborationfor important clarifications on all the items. If relevant, we also recommend reading CONSORT extensions for cluster randomised trials [bib_ref] CONSORT statement: extension to cluster randomised trials, Campbell [/bib_ref] , non-inferiority and equivalence trials [bib_ref] Reporting of noninferiority and equivalence randomized trials: an extension of the CONSORT..., Piaggio [/bib_ref] , nonpharmacological treatments [bib_ref] Extending the CONSORT statement to randomized trials of nonpharmacologic treatment: explanation and..., Boutron [/bib_ref] , herbal interventions [bib_ref] Reporting randomized, controlled trials of herbal interventions: an elaborated CONSORT statement, Gagnier [/bib_ref] , and pragmatic trials [bib_ref] Pragmatic Trials in Healthcare (Practihc) group. Improving the reporting of pragmatic trials:..., Zwarenstein [/bib_ref]. Additional extensions are forthcoming: for those and for up to date references relevant to this checklist, see http://www.consort-statement.org/.
Item 1b (title and abstract)-We added a sub-item on providing a structured summary of trial design, methods, results, and conclusions and referenced the CON-SORT for abstracts article. Item 2b (introduction)-We added a new sub-item (formerly item 5 in CONSORT 2001) on "Specific objectives or hypotheses"
Item 3a (trial design)-We added a new item including this sub-item to clarify the basic trial design (such as parallel group, crossover, cluster) and the allocation ratio Item 3b (trial design)-We added a new sub-item that addresses any important changes to methods after trial commencement, with a discussion of reasons Item 4 (participants)-Formerly item 3 in CONSORT 2001
Item 5 (interventions)-Formerly item 4 in CONSORT 2001. We encouraged greater specificity by stating that descriptions of interventions should include "sufficient details to allow replication" [bib_ref] What is missing from descriptions of treatment in trials and reviews, Glasziou [/bib_ref] Item 6 (outcomes)-We added a sub-item on identifying any changes to the primary and secondary outcome (endpoint) measures after the trial started. This followed from empirical evidence that authors frequently provide analyses of outcomes in their published papers that were not the prespecified primary and secondary outcomes in their protocols, while ignoring their prespecified outcomes (that is, selective outcome reporting) [bib_ref] Systematic review of the empirical evidence of study publication bias and outcome..., Dwan [/bib_ref] [bib_ref] Empirical evidence for selective reporting of outcomes in randomized trials: comparison of..., Chan [/bib_ref]. We eliminated text on any methods used to enhance the quality of measurements Item 9 (allocation concealment mechanism)-We reworded this to include mechanism in both the report topic and the descriptor to reinforce that authors should report the actual steps taken to ensure allocation concealment rather than simply report imprecise, perhaps banal, assurances of concealment Item 11 (blinding)-We added the specification of how blinding was done and, if relevant, a description of the similarity of interventions and procedures. We also eliminated text on "how the success of blinding (masking) was assessed" because of a lack of empirical evidence supporting the practice as well as theoretical concerns about the validity of any such assessment [bib_ref] Commentary: Measuring the success of blinding in RCTs: don't, must, can't or..., Sackett [/bib_ref] [bib_ref] Blinding in randomised trials: hiding who got what, Schulz [/bib_ref] Item 12a (statistical methods)-We added that statistical methods should also be provided for analysis of secondary outcomes Sub-item 14b (recruitment)-Based on empirical research, we added a sub-item on "Why the trial ended or was stopped"Item 15 (baseline data)-We specified "A table" to clarify that baseline and clinical characteristics of each group are most clearly expressed in a table Item 16 (numbers analysed)-We replaced mention of "intention to treat" analysis, a widely misused term, by a more explicit request for information about retaining participants in their original assigned groups [bib_ref] What is meant by intention to treat analysis? Survey of published randomised..., Hollis [/bib_ref] Sub-item 17b (outcomes and estimation)-For appropriate clinical interpretability, prevailing experience suggested the addition of "For binary outcomes, presentation of both relative and absolute effect sizes is recommended" [bib_ref] Reporting number needed to treat and absolute risk reduction in randomized controlled..., Nuovo [/bib_ref] Item 19 (harms)-We included a reference to the CON-SORT paper on harms [bib_ref] Better reporting of harms in randomized trials: an extension of the CONSORT..., Ioannidis [/bib_ref] Item 20 (limitations)-We changed the topic from "Interpretation" and supplanted the prior text with a sentence focusing on the reporting of sources of potential bias and imprecision Item 22 (interpretation)-We changed the topic from "Overall evidence." Indeed, we understand that authors should be allowed leeway for interpretation under this nebulous heading. However, the CONSORT Group expressed concerns that conclusions in papers frequently misrepresented the actual analytical results and that harms were ignored or marginalised. Therefore, we changed the checklist item to include the concepts of results matching interpretations and of benefits being balanced with harms Item 23 (registration)-We added a new item on trial registration. Empirical evidence supports the need for trial registration, and recent requirements by journal editors have fostered compliance [bib_ref] registration: a statement from the International Committee of, De Angelis [/bib_ref] Item 24 (protocol)-We added a new item on availability of the trial protocol. Empirical evidence suggests that authors often ignore, in the conduct and reporting of their trial, what they stated in the protocol [bib_ref] Systematic review of the empirical evidence of study publication bias and outcome..., Dwan [/bib_ref] [bib_ref] Empirical evidence for selective reporting of outcomes in randomized trials: comparison of..., Chan [/bib_ref]. Hence, availability of the protocol can instigate adherence to the protocol before publication and facilitate assessment of adherence after publication Item 25 (funding)-We added a new item on funding. Empirical evidence points toward funding source sometimes being associated with estimatedeatment effects [bib_ref] Pharmaceutical industry sponsorship and research outcome and quality: systematic review, Lexchin [/bib_ref] 
[table] Table 1: CONSORT 2010 checklist of information to include when reporting a randomised trial* [/table]