BMJ 1996;313:570-571 (7 September)

Editorials

Better reporting of randomised controlled trials: the CONSORT statement

Authors must provide enough information for readers to know how the trial was performed

Randomised controlled trials are the best way to compare the effectiveness of different interventions. Only randomised trials allow valid inferences of cause and effect. Only randomised trials have the potential directly to affect patient care--occasionally as single trials but more often as the body of evidence from several trials, whether or not combined formally by meta-analysis. It is thus entirely reasonable to require higher standards for papers reporting randomised trials than those describing other types of study.

Like all studies, randomised trials are open to bias if done badly.1 It is thus essential that randomised trials are done well and reported adequately. Readers should not have to infer what was probably done, they should be told explicitly. Proper methodology should be used and be seen to have been used. Yet reviews of published trials have consistently found major deficiencies in reporting,2 3 4 making the task for those carrying out systematic reviews much harder. Almost 50 years after the first publication of a randomised trial,5 the guarantee of adequate reporting of these important studies is surely long overdue.

In 1994 two groups independently published proposals for requirements for the reporting of randomised trials.6 7 In an editorial in JAMA Drummond Rennie suggested that the two groups should combine to produce a unified statement,8 and the outcome of this process was published last week.9 The new CONSORT statement lists 21 items that should be included in a report (see table 1) as well as a flow chart describing patient progress through the trial (fig 1). In addition, a few specific subheadings are suggested within the methods and results sections of the paper. In the spirit of the times, the recommendations are evidence based where possible, with common sense dictating the remainder.

Table 1   Items that should be included in reports of randomised trials (reproduced from JAMA)9

Heading Subheading Descriptor
Title Identify the study as a randomised trial
Abstract Use a structured format
Introduction State prospectively defined hypothesis, clinical objectives, and planned subgroup or covariate analyses
Methods Protocol Describe
Planned study population, together with inclusion or exclusion criteria
Planned interventions and their timing
Primary and secondary outcome measure(s) and the minimum important difference(s), and indicate how the target sample size was projected
Rationale and methods for statistical analyses, detailing main comparative analyses and whether they were completed on an intention to treat basis
Prospectively defined stopping rules (if warranted)
Assignment Describe
Unit of randomisation (for example, individual, cluster, geographic)
Method used to generate the allocation schedule
Method of allocation concealment and timing of assignment
Method to separate the generator from the executor of assignment
Masking (blinding) Describe
Mechanism (for example, capsules, tablets)
Similarity of treatment characteristics (for example, appearance, taste)
Allocation schedule control (location of code during trial and when broken)
Evidence for successful blinding among participants, person doing intervention, outcome assessors, and data analysts
Results Participant flow and follow up Provide a trial profile (Fig 1) summarising participant flow, numbers and timing of randomisation assignment, interventions, and measurements for each randomised group
Analysis State estimated effect of intervention on primary and secondary outcome measures, including a point estimate and measure of precision (confidence interval)
State results in absolute numbers when feasible (for example, 10/20, not 50%)
Present summary data and appropriate descriptive and interferential statistics in sufficient detail to permit alternative analyses and replication
Describe prognostic variables by treatment group and any attempt to adjust for them
Describe protocol deviations from the study as planned, together with the reasons
Discussion State specific interpretations of study findings, including sources of bias and imprecision (internal validity) and discussion of external validity, including appropriate quantitative measures when possible
State general interpretation of the data in light of the totality of the available evidence



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  		Fig 1--Flow chart describing progress of patients through randomised trial (reproduced from JAMA)9

In essence the requirement is that authors should provide enough information for readers to know how the trial was performed so that they can judge whether the findings are likely to be reliable. The CONSORT statement means that authors will no longer be able to hide inadequacies in their study by omitting important information. For example, at present authors can, and often do, hide their procedures behind the single word "randomised." Authors will now be required to give details of the randomisation procedure. If authors have used an inferior approach, such as alternate allocation, they will have to say so. The BMJ has in fact refused to publish trials that were not truly randomised since 1991,10 a position justified by subsequent empirical findings.1

As the authors of the CONSORT statement note,9 the checklist applies to the most common design of randomised trial--trials with two parallel groups. Some modification is needed for special types of trial such as crossover trials and those with more than two treatment groups. Also, the list should be taken in conjunction with existing general requirements--for example, the requirement to specify all statistical methods used in the analysis. This and other items appear on the checklist for controlled trials that has been used by the BMJ's statistical referees for over 10 years.11

Some of the items on the checklist would benefit from greater explanation than is possible in the CONSORT statement. In time a fuller accompanying explanatory paper could be valuable. For example, while the advantages of randomisation have been apparent for several decades, understanding the rationale for it remains poor and so its importance is not fully appreciated by researchers.12

The BMJ supports the CONSORT statement and is adopting its recommendations. So too are JAMA, Lancet, and some other journals. Trialists are encouraged to follow the statement right away, but from 1 January 1997 they will be required to do so. Authors should submit with their papers a copy of the completed checklist indicating on which page of the manuscript each item is addressed. The checklist will be used by the editors and supplied to referees. In the published papers the BMJ will use the additional subheadings suggested by CONSORT.

It seems reasonable to hope that, in addition to improved reporting, the wide adoption of this new publication standard will improve the conduct of future research by increasing awareness of the requirements for a good trial. Such success might lead to similar initiatives for other types of research.

DOUGLAS G ALTMAN Head ICRF Medical Statistics Group, Centre for Statistics in Medicine, Institute of Health Sciences, Oxford OX3 7LF

Douglas G Altman 

  1. Schulz KF, Chalmers I, Hayes R, Altman DG. Empirical evidence of bias. Dimensions of methodological quality associated with estimates of treatment effects in controlled trials. JAMA 1995;273:408-12. [Abstract]
  2. Mosteller F, Gilbert JP, McPeek B. Reporting standards and research strategies for controlled trials. Agenda for the editor. Controlled Clin Trials 1980;1:37-58.
  3. Pocock SJ, Hughes MD, Lee RJ. Statistical problems in the reporting of clinical trials. N Engl J Med 1987;317:426-32. [Abstract]
  4. Schulz KF, Chalmers I, Grimes DA, Altman DG. Assessing the quality of randomization from reports of controlled trials published in obstetrics and gynecology journals. JAMA 1994;272:125-8. [Abstract]
  5. Medical Research Council. Streptomycin treatment of pulmonary tuberculosis. BMJ 1948;ii:769-82.
  6. Standards of Reporting Trials Group. A proposal for structured reporting of randomized controlled trials. JAMA 1994;272:1926-31. [Medline]
  7. Working Group on Recommendations for Reporting of Clinical Trials in the Biomedical Literature. Call for comments on a proposal to improve reporting of clinical trials in the biomedical literature: a position paper. Ann Intern Med 1994;121:894-5. [Free Full Text]
  8. Rennie D. Reporting randomised controlled trials: an experiment and a call for responses from readers. JAMA 1995;273:1054-5. [Medline]
  9. Begg C, Cho M, Eastwood S, Horton R, Moher D, Olkin I, et al. Improving the quality of reporting of randomized controlled trials: the CONSORT statement. JAMA 1996;276:637-9. [Medline]
  10. Altman DG. Randomisation. BMJ 1991;302:1481-2.
  11. Gardner MJ, Machin D, Campbell MJ. The use of checklists in assessing the statistical content of medical studies BMJ 1986;292:810-2.
  12. Schulz KF. Subverting randomization in controlled trials. JAMA 1996;274:1456-8.

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