Review Schulz et al.
Open Medicine 2010;4(1):e60
CONSORT 2010 Statement: updated guidelines
for reporting parallel group randomized trials
Kenneth F Schulz, DouglaS g altman, DaviD moher; For the conSort group
Kenneth F Schulz is distinguished scientist and vice president, Family Health International, Research Triangle Park, North Carolina, U.S.
Douglas G Altman is professor, Centre for Statistics in Medicine, University of Oxford, Wolfson College, Oxford, England. David Moher is senior
scientist, Ottawa Methods Centre, Clinical Epidemiology Program, Ottawa Hospital Research Institute, Department of Epidemiology and Com-
munity Medicine, University of Ottawa, Ottawa, Ontario, Canada.
Funding: We received nancial support from United Kingdom National Institute for Health Research and the Medical Research Council; Canadi-
an Institutes of Health Research; Presidents Fund, Canadian Institutes of Health Research; Johnson & Johnson; BMJ; and the American Society
for Clinical Oncology. Douglas Altman is supported by Cancer Research UK, David Moher by a University of Ottawa Research Chair and Kenneth
Schulz by Family Health International. None of the sponsors had any involvement in the planning, execution or writing of the CONSORT docu-
ments. Additionally, no funder played a role in drafting the manuscript.
Competing interests: Uniform disclosure of potential conicts of interest: all authors have completed the ICMJE unied competing interest
form at www.icmje.org/coi_disclosure.pdf (available from the corresponding author) and declare (1) David Moher received grants for this work
from Johnson & Johnson, BMJ, and American Society for Clinical Oncology; Kenneth Schulz and Douglas Altman received support for travel to
meetings for this work from Johnson & Johnson, BMJ, and American Society for Clinical Oncology; (2) Kenneth Schulz and Douglas Altman had
travel expenses reimbursed by the EQUATOR Network; Kenneth Schulz has received honoraria for delivering educational presentations for the
American Board of Obstetrics and Gynecology Foundation for Excellence in Women’s Health Care, Ortho-McNeil Janssen Scientic Affairs, and
the American College of Obstetrics and Gynecology; and has done consultancy for Wyeth. All authors also declare (3) no spouses, partners, or
children with relationships with commercial entities that might have an interest in the submitted work; (4) no non-nancial interests that may
be relevant to the submitted work.
Correspondence: K F Schulz, kschulz@fhi.org
R
andomized controlled trials, when they
are appropriately designed, conducted and
reported, represent the gold standard in evalu-
ating health care interventions. However, randomized
trials can yield biased results if they lack methodological
rigour.
1
To assess a trial accurately, readers of a published
report need complete, clear and transparent informa-
tion on its methodology and ndings. Unfortunately, at-
tempted assessments frequently fail because authors of
many trial reports neglect to provide lucid and complete
descriptions of that critical information.
2–4
That lack of adequate reporting fuelled the develop-
ment of the original CONSORT (Consolidated Standards
of Reporting Trials) statement in 1996
5
and its revision 5
years later.
6–8
While those statements improved the re-
porting quality for some randomized controlled trials,
9, 10
many trial reports still remain inadequate.
2
Further-
more, new methodological evidence and additional ex-
perience has accumulated since the last revision in 2001.
Consequently, we organized a CONSORT Group meeting
to update the 2001 statement.
6–8
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 (see Table 1) and the
ow diagram (see Fig. 1). It provides guidance for re-
porting all randomized controlled trials, but focuses on
the most common design type—individually random-
ized, 2-group parallel trials. Other trial designs, such
as cluster randomized trials and non-inferiority trials,
require varying amounts of additional information.
CONSORT extensions for these designs,
11, 12
and other
CONSORT products, can be found through the CON-
SORT website (www.consort-statement.org). Along
with the CONSORT statement, we have updated the
explanation and elaboration article,
13
which explains
the inclusion of each checklist item, provides methodo-
logical background and gives published examples of
transparent reporting.
Diligent adherence by authors to the checklist items
facilitates clarity, completeness and transparency of re-
porting. Explicit descriptions, not ambiguity or omis-
sion, best serve the interests of all readers. Note that the
Open Medicine 2010;4(1):e61
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CONSORT 2010 Statement does not include recommen-
dations for designing, conducting and analyzing 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 deciencies
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 pro-
cess without revelation of their trial’s inadequacies. That
emerging reality should provide impetus to improved
trial design and conduct in the future, a secondary in-
direct goal of our work. Moreover, CONSORT can help
researchers in designing their trial.
Background to CONSORT
Efforts to improve the reporting of randomized con-
trolled trials accelerated in the mid-1990s, spurred part-
ly 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.
14
Two initiatives aimed at de-
veloping reporting guidelines culminated in one of us
(DM) and Drummond Rennie organizing the rst CON-
SORT statement in 1996.
5
Further methodological re-
search on similar topics reinforced earlier ndings
15
and
fed into the revision of 2001.
6–8
Subsequently, the ex-
panding body of methodological research informed the
renement of CONSORT 2010. More than 700 studies
comprise the CONSORT database (located on the CON-
SORT website), which provides the empirical evidence to
underpin the CONSORT initiative.
Indeed, CONSORT Group members continually mon-
itor the literature. Information gleaned from these ef-
forts 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 bio-
medical editors. The CONSORT Executive (KFS, DGA,
DM) strives for a balance of established and emerging
Assessed for eligibility (n = ... )
Randomized (n = ... )
Allocated to intervention (n = ... )
Received allocated intervention (n = ... )
Did not receive allocated intervention
(give reasons) (n = ... )
Allocated to intervention (n = ... )
Received allocated intervention (n = ... )
Did not receive allocated intervention
(give reasons) (n = ... )
Lost to follow-up (give reasons) (n = ... )
Discontinued intervention (give reasons) (n = ... )
Lost to follow-up (give reasons) (n = ... )
Discontinued intervention (give reasons) (n = ... )
Analyzed (n = ...)
Discontinued from analysis (give reasons) (n = ... )
Analyzed (n = ...)
Discontinued from analysis (give reasons) (n = ... )
Excluded (n = ... )
Not meeting inclusion criteria (n = ... )
Declined to participate (n = ... )
Other reasons (n = ... )
Enrolment
Allocation
Follow-up
Analysis
Figure 1: Flow diagram of the progress through the phases of a parallel randomized trial of 2 groups
(that is, enrolment, intervention allocation, follow-up, and data analysis).
Open Medicine 2010;4(1):e62
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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 con-
tribute. As such, CONSORT continually assimilates new
ideas and perspectives. That process informs the con-
tinually 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 health care journals
support it without our knowledge. Moreover, thousands
more have implicitly supported it with the endorsement
of the CONSORT statement by the International Com-
mittee of Medical Journal Editors (www.icmje.org).
Other prominent editorial groups, the Council of Science
Editors and the World Association of Medical Editors,
ofcially support CONSORT. That support seems war-
ranted: when used by authors and journals, CONSORT
seems to improve reporting.
9
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 accumulat-
ing evidence relating to existing checklist items, several
new issues had come to prominence since 2001. Some
participants were given primary responsibility for aggre-
gating and synthesizing the relevant evidence on a par-
ticular 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 randomized con-
trolled 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 instruc-
tions 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 inclu-
sion at this point. The CONSORT 2010
Statement thus addresses the minimum
criteria, although that should not deter
authors from including other informa-
tion if they consider it important.
After the meeting, the CONSORT
Executive convened teleconferences
and meetings to revise the checklist. After 7 major iter-
ations, 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 rst draft of this paper, which was
then distributed to the group for feedback. After con-
sideration of their comments, the executive nalized
the statement.
The CONSORT Executive then drafted an updated ex-
planation 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 addi-
tions, deletions and changes. That nal iterative pro-
cess converged to the CONSORT 2010 Explanation and
Elaboration.
13
Changes in CONSORT 2010
The revision process resulted in evolutionary, not revo-
lutionary, changes to the checklist (Table 1), and the
ow diagram was not modied except for 1 word (Fig.
1). Moreover, because other reporting guidelines aug-
menting 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 addi-
tional 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 summarized the noteworthy general
changes in Box 1 and specic changes in Box 2. The CON-
SORT website contains a side-by-side comparison of the
2001 and 2010 versions.
Box 1: Noteworthy general changes in CONSORT 2010 Statement
• We simpli ed and clari ed the wording, such as in items 1, 8, 10, 13, 15, 16, 18,
19 and 21.
• We improved consistency of style across the items by removing the
imperative verbs that were in the 2001 version.
• We enhanced speci city 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 di culties 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 set-
tings and locations. CONSORT 2010 relieves obfuscations and forces authors
to provide page numbers in the checklist for both eligibility and settings.
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Implications and limitations
We developed CONSORT 2010 to assist authors in writ-
ing reports of randomized controlled trials, editors and
peer reviewers in reviewing manuscripts for publication,
and readers in critically appraising published articles.
The CONSORT 2010 Explanation and Elaboration pro-
vides elucidation and context to the checklist items. We
strongly recommend using the explanation and elabora-
tion 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 2-group,
parallel randomized controlled trial, which accounts
for over half of trials in the literature.
2
Most of the items
from the CONSORT 2010 Statement, however, pertain to
all types of randomized 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 (amplications),
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 re-
views and meta-analyses of studies evaluating interven-
tions,
16
diagnostic studies,
17
and observational studies.
18
The explicit goal of all these initiatives is to improve re-
porting. The Enhancing the Quality and Transparency of
Health Research (EQUATOR) Network will facilitate de-
velopment of reporting guidelines and help disseminate
the guidelines: www.equator-network.org provides in-
formation on all reporting guidelines in health research.
With CONSORT 2010, we again intentionally declined
to produce a rigid structure for the reporting of random-
ized trials. Indeed, SORT
19
tried a rigid format, and it
failed in a pilot run with an editor and authors.
20
Con-
sequently, the format of articles should abide by journal
style, editorial directions, the traditions of the research
eld addressed, and, where possible, author preferences.
We do not wish to standardize the structure of reporting.
Authors should simply address checklist items some-
where in the article, with ample detail and lucidity. That
stated, we think that manuscripts benet from frequent
subheadings within the major sections, especially the
methods and results sections.
CONSORT urges completeness, clarity and transparen-
cy of reporting, which simply reects the actual trial design
and conduct. However, as a potential drawback, a re-
porting guideline might encourage some authors to report
ctitiously the information suggested by the guidance rath-
er 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 infor-
mation on trial registers and to regulatory agency websites.
Moreover, the CONSORT 2010 Statement does not include
recommendations for designing and conducting random-
ized 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, CONSORT 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 scru-
tiny of any weak aspects of their trials. However, with
wide adoption of CONSORT by journals and editorial
groups, most authors should have to report transparent-
ly all important aspects of their trial. The ensuing scru-
tiny rewards well-conducted trials and penalizes 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 specically requested otherwise.
Journals that do not currently support CONSORT may do
so by registering on the CONSORT website. If a journal sup-
ports 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 auth-
ors who wish to cite CONSORT should cite this or another
of the original journal versions of CONSORT 2010 State-
ment, and, if appropriate, the CONSORT 2010 Explanation
and Elaboration.
13
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
rst consult the CONSORT policy statement on the website.
We emphasize that CONSORT 2010 represents an
evolving guideline. It requires perpetual reappraisal
and, if necessary, modications. In the future we will
further revise the CONSORT material considering com-
ments, criticisms, experiences and accumulating new
evidence. We invite readers to submit recommendations
via the CONSORT website.
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Box 2: Noteworthy specifi c changes in CONSORT 2010 Statement
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 CONSORT for abstracts article
21
Item 2b (introduction) We added a new sub-item (formerly item 5 in CONSORT 2001) on “Speci c 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 speci city by stating that descriptions
of interventions should include “su cient details to allow replication”
3
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 pre-speci ed
primary and secondary outcomes in their protocols, while ignoring their pre-speci ed outcomes
(that is, selective outcome reporting).
4,22
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 speci cation 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
23,24
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”
25
Item 15 (baseline data) We speci ed “A table” to clarify that baseline and clinical characteristics of each group are most
clearly expressed in a table
Item 16 (numbers analyzed) 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
26
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 e ect sizes is recommended”
27
Item 19 (harms) We included a reference to the CONSORT paper on harms
28
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 marginalized. Therefore, we changed the checklist item to
include the concepts of results matching interpretations and of bene ts 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
29
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.
4,22
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 estimated treatment e ects
30
