The Revised CONSORT Statement for Reporting Randomized Trials: Explanation and Elaboration

The RCT is a very beautiful technique, of wide applicability, but as with everything else there are snags. When humans have to make observations there is always the possibility of bias (1). Well-designed and properly executed randomized, controlled trials (RCTs) provide the best evidence on the efficacy of health care interventions*, but trials with inadequate methodologic approaches are associated with exaggerated treatment effects (2-5). Biased* results from poorly designed and reported trials can mislead decision making in health care at all levels, from treatment decisions for the individual patient to formulation of national public health policies. Critical appraisal of the quality of clinical trials is possible only if the design, conduct, and analysis of RCTs are thoroughly and accurately described in published articles. Far from being transparent, the reporting of RCTs is often incomplete (6-9), compounding problems arising from poor methodology (10-15). Incomplete and Inaccurate Reporting Many reviews have documented deficiencies in reports of clinical trials. For example, information on whether assessment of outcomes* was blinded was reported in only 30% of 67 trial reports in four leading journals in 1979 and 1980 (16). Similarly, only 27% of 45 reports published in 1985 defined a primary end point* (14), and only 43% of 37 trials with negative findings published in 1990 reported a sample size* calculation (17). Reporting is not only frequently incomplete but also sometimes inaccurate. Of 119 reports stating that all participants* were included in the analysis in the groups to which they were originally assigned (intention-to-treat* analysis), 15 (13%) excluded patients or did not analyze all patients as allocated (18). Many other reviews have found that inadequate reporting was common in specialty journals (19-29) and journals published in languages other than English (30, 31). Proper randomization* eliminates selection bias* and is the crucial component of high-quality RCTs (32) Successful randomization hinges on two steps: generation* of an unpredictable allocation sequence and concealment* of this sequence from the investigators enrolling participants (Table 1) (2, 21). Unfortunately, reporting of the methods used for allocation of participants to interventions is also generally inadequate. For example, at least 5% of 206 reports of supposed RCTs in obstetrics and gynecology journals described studies that were not truly randomized (21). This estimate is conservative, as most reports do not at present provide adequate information about the method of allocation (19, 21, 23, 25, 30, 39). Table 1. Treatment Allocation. What's So Special about Randomization? Improving the Reporting of RCTs: The CONSORT Statement DerSimonian and colleagues (16) suggested that editors could greatly improve the reporting of clinical trials by providing authors with a list of items that they expected to be strictly reported. Early in the 1990s, two groups of journal editors, trialists, and methodologists independently published recommendations on the reporting of trials (40, 41). In a subsequent editorial, Rennie (42) urged the two groups to meet and develop a common set of recommendations; the outcome was the CONSORT statement (Consolidated Standards of Reporting Trials) (43). The CONSORT statement (or simply CONSORT) comprises a checklist of essential items that should be included in reports of RCTs and a diagram for documenting the flow of participants through a trial. It is aimed at first reports of two-group parallel designs. Most of CONSORT is also relevant to a wider class of trial designs, such as equivalence, factorial, cluster, and crossover trials. Modifications to the CONSORT checklist for reporting trials with these and other designs are in preparation. The objective of CONSORT is to facilitate critical appraisal and interpretation of RCTs by providing guidance to authors about how to improve the reporting of their trials. Peer reviewers and editors can also use CONSORT to help them identify reports that are difficult to interpret and those with potentially biased results. However, CONSORT was not meant to be used as a quality assessment instrument. Rather, the content of CONSORT focuses on items related to the internal and external validity* of trials. Many items not explicitly mentioned in CONSORT should also be included in a report, such as information about approval by an ethics committee, obtaining of informed consent from participants, existence of a data safety and monitoring committee, and sources of funding. In addition, other aspects of a trial should be properly reported, such as information pertinent to cost-effectiveness analysis (44-46) and quality-of-life assessments (47). The Revised CONSORT Statement: Explanation and Elaboration Since its publication in 1996, CONSORT has been supported by an increasing number of journals (48-51) and several editorial groups, including the International Committee of Medical Journal Editors (the Vancouver Group) (52). Evidence is accumulating that the introduction of CONSORT has improved the quality of reports of RCTs (53, 54). However, CONSORT is an ongoing initiative, and the statement is revised periodically (3). The 1996 version of the statement (43) received much comment and some criticism. For example, Meinert (55) pointed out that the terminology used lacked clarity and that the information presented in the flow diagram was incomplete. Work on a revised statement started in 1999; the revised checklist is shown in Table 2 and the revised flow diagram in Figure 1 (56-58). Table 2. Checklist of Items To Include When Reporting a Randomized Trial Figure 1. Revised template of the CONSORT ( Con solidated S tandards o f R eporting T rials) diagram showing the flow of participants through each stage of a randomized trial . During revision, it became clear that explanation and elaboration of the principles underlying the CONSORT statement would help investigators and others to write or appraise trial reports. In this article, we discuss the rationale and scientific background for each item (Table 2) and provide published examples of good reporting. (For further examples, see www.consort-statement.org). In these examples, we have removed authors' references to other publications to avoid confusion; however, relevant references should always be cited where needed, such as to support unfamiliar methodologic approaches. Where possible, we describe the findings of relevant empirical studies. Many excellent books on clinical trials offer fuller discussion of methodologic issues (59-61). For convenience, we sometimes refer to treatments and patients, although we recognize that not all interventions evaluated in RCTs are technically treatments and the participants in trials are not always patients. Checklist Items Title and Abstract ITEM 1. How participants were allocated to interventions (e.g., random allocation, randomized, or randomly assigned). Examples Title: Smoking reduction with oral nicotine inhalers: double blind, randomised clinical trial of efficacy and safety (62). Abstract: Design: Randomized, double-blind, placebo-controlled trial (63). Explanation The ability to identify a relevant report in an electronic database depends to a large extent on how it was indexed. Indexers for the National Library of Medicine's MEDLINE database may not classify a report as an RCT if the authors do not explicitly report this information. To help ensure that a study is appropriately indexed as an RCT, authors should state explicitly in the abstract of their report that the participants were randomly assigned to the comparison groups. Possible wordings include participants were randomly assigned to , treatment was randomized, or participants were assigned to interventions by using random allocation. We also strongly encourage the use of the word randomized in the title of the report to permit instant identification. In the mid-1990s, electronic searching of MEDLINE yielded only about half of all RCTs relevant to a topic (64). This deficiency has been remedied in part by the work of the Cochrane Collaboration, which by 1999 had identified almost 100 000 RCTs that had not been indexed as such in MEDLINE. These reports have been reindexed (65). Adherence to this recommendation should improve the accuracy of indexing in the future. We encourage the use of structured abstracts when a summary of the report is required. Structured abstracts provide readers with a series of headings pertaining to the design, conduct, and analysis of a trial; standardized information appears under each heading (66). Some studies have found that structured abstracts are of higher quality than the more traditional descriptive abstracts (67) and that they allow readers to find information more easily (68). Introduction ITEM 2. Scientific background and explanation of rationale. Example The carpal tunnel syndrome is caused by compression of the median nerve at the wrist and is a common cause of pain in the arm, particularly in women. Injection with corticosteroids is one of the many recommended treatments. One of the techniques for such injection entails injection just proximal to (not into) the carpal tunnel. The rationale for this injection site is that there is often a swelling at the volar side of the forearm, close to the carpal tunnel, which might contribute to compression of the median nerve. Moreover, the risk of damaging the median nerve by injection at this site is lower than by injection into the narrow carpal tunnel. The rationale for using lignocaine (lidocaine) together with corticosteroids is twofold: the injection is painless, and diminished sensation afterwards shows that the injection was properly carried out. We investigated in a double blind randomised trial, firstly, whether symptoms disappeared after injection with corticosteroids proximal to the carpal tunnel and, secondly, how ma