The
Cochrane Collaboration Logo |
|
| The Cochrane
Collaboration logo illustrates a systematic review of
data from seven randomized
controlled trials (RCTs), comparing one health care
treatment with a placebo. Each horizontal line represents
the results of one trial (the shorter the line, the more
certain the result); and the diamond represents their
combined results. The vertical line indicates the
position around which the horizontal lines would cluster
if the two treatments compared in the trials had similar
effects; if a horizontal line touches the vertical line,
it means that that particular trial found no clear
difference between the treatments. The position of the
diamond to the left of the vertical line indicates that
the treatment studied is beneficial. Horizontal lines or
a diamond to the right of the line would show that the
treatment did more harm than good. |
| This diagram shows the
results of a systematic review of RCTs of a short,
inexpensive course of a corticosteroid given to women
about to give birth too early. The first of these RCTs
was reported in 1972. The diagram summarises the evidence
that would have been revealed had the available RCTs been
reviewed systematically a decade later: it indicates
strongly that corticosteroids reduce the risk of babies
dying from the complications of immaturity. By 1991,
seven more trials had been reported, and the picture had
become still stronger. This treatment reduces the odds of
the babies of these women dying from the complications of
immaturity by 30 to 50 per cent. |
| Because no systematic
review of these trials had been published until 1989,
most obstetricians had not realised that the treatment
was so effective. As a result, tens of thousands of
premature babies have probably suffered and died
unnecessarily (and needed more expensive treatment than
was necessary). This is just one of many examples of the
human costs resulting from failure to perform systematic,
up-to-date reviews of RCTs of health care. |
| |
Archie Cochrane |
| Health care
professionals, consumers, researchers, and policy makers
are over-whelmed with unmanageable amounts of
information. In an influential book published in 1972
(Cochrane, 1972), Archie Cochrane, a British
epidemiologist, drew attention to our great collective
ignorance about the effects of health care. He
recognised that people who want to make more informed
decisions about health care do not have ready access to
reliable reviews of the available evidence. In
1979, he wrote (Cochrane, 1979): |
| "It is surely a
great criticism of our profession that we have not
organised a critical summary, by specialty or
subspecialty, adapted periodically, of all relevant
randomized controlled trials". |
| In 1987, the year before
Cochrane died, he referred to a systematic review
of randomized controlled trials (RCTs) of care
during pregnancy and childbirth as "a real milestone
in the history of randomized trials and in the evaluation
of care", and suggested that other specialties
should copy the methods used (Cochrane, 1989). In the
same year, the scientific quality of many published
reviews was shown to leave much to be desired (Mulrow,
1987). As Cochrane had emphasised, reviews of
research evidence must be prepared systematically and
they must be kept up-to-date to take account of new
evidence. |
| If this is not done,
important effects of health care (good and bad) will not
be identified promptly, and people using the health
services will be ill-served as a result. In addition,
without systematic, up-to-date reviews of previous
research, plans for new research will not be well
informed. As a result, researchers and funding bodies
will miss promising leads, and embark on studies asking
questions that have already been answered (Chalmers,
1992). |
| |
The
Cochrane Collaboration |
| The Cochrane
Collaboration has developed in response to
Cochrane’s call for systematic, up-to-date reviews
of all relevant RCTs of health care. Cochrane’s
suggestion that the methods used to prepare and maintain
reviews of controlled trials in pregnancy and childbirth
should be applied more widely was taken up by the
Research and Development Programme, initiated to support
the United Kingdom’s National Health Service. Funds
were provided to establish a ‘Cochrane Centre’,
to collaborate with others, in the UK and elsewhere, to
facilitate systematic reviews of randomized controlled
trials across all areas of health care [Antman, 1992;
Chalmers, 1997). |
| When ‘The Cochrane
Centre’ was opened, in Oxford, in October 1992,
those involved expressed the hope that there would be a
collaborative international response to Cochrane’s
agenda. This idea was outlined at a meeting organised six
months later by the New York Academy of Sciences
(Chalmers, 1993). In October 1993 - at what was to become
the first in a series of annual Cochrane Colloquia - 77
people from nine countries co-founded ‘The Cochrane
Collaboration’. |
| |
The Eight Values of the Cochrane Collaboration |
| The Cochrane
Collaboration has evolved rapidly since it was
inaugurated at the 1st Colloquium, but its basic
objectives and principles have remained the same as they
were at its inception. It is an international
organization that aims to help people make well informed
decisions about health care by preparing, maintaining and
ensuring the accessibility of systematic reviews of the
effects of health care interventions. The Collaboration
is being built on eight values: |
| · collaboration |
| · building on the
enthusiasm of individuals |
| · avoiding duplication |
| · minimizing bias |
| · keeping up to date |
| · ensuring relevance |
| . ensuring access |
| · continually improving
the quality of its work |
| |
Collaborative Reviews Groups |
| Cochrane reviews (the
principal output of the Collaboration) are published
electronically in successive issues of The Cochrane
Database of Systematic Reviews. Preparation and
maintenance of Cochrane reviews is the responsibility of
international collaborative review groups. At the
beginning of 1997, the existing and planned review groups
(over 40) cover most of the important areas of health
care. The members of these groups - researchers,
health care professionals, consumers, and others - share
an interest in generating reliable, up-to-date evidence
relevant to the prevention, treatment and rehabilitation
of particular health problems or groups of problems. How
can stroke and its effects be prevented and treated? What
drugs should be used to prevent and treat malaria,
tuberculosis and other important infectious diseases?
What strategies are effective in preventing brain and
spinal cord injury and its consequences, and what
rehabilitative measures can help those with residual
disabilities? |
| Each collaborative
review group is required to prepare a plan outlining how
it will contribute to the Collaboration’s
objectives. This plan is developed in consultation with
the staff of one or more Cochrane centres (which,
collectively, share responsibility for co-ordinating the
development of the Collaboration). A collaborative review
group’s plan of work must be based on agreements
reached at one or more exploratory meetings of those
interested in becoming involved in the group. The plan
defines the scope of the group and the specific topics
falling within the scope. It describes who will have
responsibility for planning, co-ordinating and monitoring
the group’s work (a co-ordinating editor, supported
by an editorial team). It describes how the group will
identify and assemble in a specialised register as high a
proportion as possible of all the studies relevant to its
declared scope; and who, drawing on the studies in the
register, will take responsibility for preparing and
maintaining which reviews. Every group appoints an
individual to organise and manage the day-to-day
activities of the group, who is based at the same place
as the co-ordinating editor. |
| Members of collaborative
review groups are helped to tackle these various tasks
through training materials developed by the Collaboration
(Mulrow, 1994) and through training workshops organised
by Cochrane centres (and sometimes by the groups
themselves). Whenever possible, training for people
preparing and maintaining Cochrane reviews is based on
the results of empirical research. Such
methodological research is the focus of individuals who
have come together in Cochrane methods working
groups. |
| |
Cochrane Methods Working Groups |
| As they carry out their
review, reviewers employ a series of methods to assemble,
appraise, and sometimes synthesize data from the trials
that are relevant to their question. In doing so, they
draw on the work of Cochrane methods working
groups, which are created to organise and disseminate the
work of methodologists who have come together to
improve the validity and precision of systematic reviews.
For example, collaborative review groups benefit from a
methods working group which developed high-quality,
uniform methods for hand-searching journals. Members from
a number of methods working groups have played major
roles in the creation and maintenance of the Review
Manager (or ‘RevMan’) software that helps
reviewers organise, prepare, analyse, and present their
systematic reviews. |
| |
Cochrane Fields |
| Fields are Cochrane
groupings that focus on dimensions of health care other
than health problems, such as the setting of care (e.g.
primary care), the type of consumer (e.g. older people),
the type of provider (e.g. nurses) or the type of
intervention (e.g. physical therapies). People working in
fields handsearch specialist journals, help to ensure
that priorities and perspectives in their field of
interest are reflected in the work of collaborative
review groups, compile specialist databases of reviews,
co-ordinate activities with relevant agencies outside the
Collaboration, and comment on systematic reviews relating
to their particular area. |
| |
Cochrane Centres |
| The work of the Cochrane
groupings described above is facilitated in a variety of
ways by the work of Cochrane centres. The characteristics
of each Cochrane centre reflect the interests of the
individuals associated with it and the resources made
available to them; but all centres share a responsibility
for helping to co-ordinate and support the Cochrane
Collaboration. The responsibilities include: |
| a) maintaining a
directory of people contributing to the Collaboration,
with information about their individual responsibilities
and interests |
| b) helping to establish
and support collaborative review groups, by fostering
international collaboration among people with similar
interests, participating in exploratory discussions and
meetings, helping to organise workshops, and in other
ways facilitating collaboration |
| c) co-ordinating
handsearches of the general health care journals and
monitoring and assisting review groups searching
specialist literature published within the geographical
area served by the Centre |
| d) co-ordinating the
Collaboration's contributions to the creation and
maintenance of an international register of completed and
ongoing RCTs, thus facilitating the first phase of data
collection for reviewers |
| e) helping - by
developing successive editions of the Collaboration's
guidelines and software - to systematise and facilitate
the preparation and updating of systematic reviews |
| f) exploring ways of
helping the public, health service providers and
purchasers, policy makers and the press to make full use
of Cochrane reviews |
| g) organising workshops,
seminars and Colloquia to support and guide the
development of the Cochrane Collaboration |
| The Cochrane centres are
not directly responsible for preparing and maintaining
systematic reviews. This is the responsibility of
collaborative review groups which also maintain registers
of systematic reviews currently being prepared or
planned, so that unnecessary duplication of effort can be
minimised and collaboration promoted. |
| |
Consumer Participation |
| Consumers participate
throughout most of the organisation. Collaborative review
groups, fields and Cochrane centres all seek input and
feedback from consumers, which the Cochrane Collaboration
considers essential in order to fulfil its goals. |
| The Consumer Network has
been established to reflect consumer interests within the
Cochrane Collaboration. The basis for the network is a
belief that involvement by consumers in the work of the
Collaboration is important, and that this involvement
will be enhanced by collaboration between consumers and
others. The Consumer Network aims to: |
| a) provide information
and a forum for networking among consumers involved in
the Collaboration |
| b) support the
involvement of consumers throughout the Cochrane
Collaboration's activities |
| c) provide mechanisms of
accountability for consumer representatives in the
Collaboration |
| d) liaise with consumer
groups around the world |
| e) encourage more
consumers to become involved in the Collaboration, and
use its products. |
| Membership of the
Consumer Network is open to individuals and is, as in all
Collaboration groupings, free of charge. |
| |
The Cochrane Library |
| To provide both an
organizational and analytical framework for assembling
Cochrane reviews in electronic format, software has been
developed by the Collaboration. Software, called
Review Manager (RevMan), is used by those preparing and
maintaining reviews; Module Manager (ModMan) enables the
editorial team to assemble protocols and complete reviews
prepared by the members of their collaborative review
group, as well as information about the collaborative
review group itself. This additional information
includes, for example, the scope of the group’s work
and the strategy it uses to assemble and maintain a
specialised register of relevant studies, derived both
from its own searching activities and from the central
Cochrane Controlled Trials Register (to which the group
will also be contributing records). |
| These
‘modules’ of Cochrane reviews and information
about the collaborative review groups, together with
modules from all the other groupings registered as
contributors to the Collaboration (centres, fields,
methods working groups, and the Consumer Network) are
submitted at intervals to the Collaboration’s Parent
Database. It is from this continuously updated Parent
Database that Cochrane reviews and information about the
Cochrane Collaboration is derived for electronic
publication in The Cochrane Library. |
Several databases are
included in The Cochrane Library. One of them, The
Cochrane Database of Systematic Reviews, contains
Cochrane reviews and another, The Cochrane Controlled
Trials Register, is a bibliographic database of
controlled trials. The Database of Abstracts of Reviews
of Effectiveness (DARE) includes structured abstracts of
systematic reviews which have been critically appraised
by reviewers at the NHS Centre for Reviews and
Dissemination in York and by other people, e.g. from the
American College of Physicians’ Journal Club and the
journal Evidence-Based Medicine. The Cochrane Review
Methodology Database is a bibliography of articles on the
science of research synthesis.
Also included in The
Cochrane Library is a Handbook on the science of
reviewing research; a Glossary of methodological terms
and Cochrane jargon; and contact details for review
groups and other groupings in the Cochrane Collaboration. |
| |
The Cochrane Database of Systematic Reviews |
| To ensure that the
results of their work can be widely disseminated,
reviewers contribute their reviews to The Cochrane
Database of Systematic Reviews on the understanding that
no one will have exclusive copyright of the
reviews. Each review incorporated in the Database
consists of: |
| a) a ‘cover
sheet’, giving the title and citation details of the
review; the names of the reviewers; the address and other
contact details of the primary reviewer, and the
editorial team responsible for the collaborative review
group to which the reviewer(s) belong(s); and the sources
of support for preparing and updating the review an
abstract |
| b) a structured report
of the review, consisting of an Introduction/statement of
objectives; information about the Materials and Methods
used; the Results of the systematic review; and a
Discussion section discussion of the results of the
analysis judgements about the implications for practice
and research |
| c) full citations of
reports of the studies incorporated in the review, and of
reports of those studies that were potentially eligible,
but which the reviewer(s) decided to exclude (giving
reasons for the exclusions) |
| d) tables of the
characteristics of the studies included in the review,
including information relevant to an assessment of the
methodological quality of each of the studies included |
| e) tables of the results
of the review, with presentation of the statistical
syntheses (meta-analyses), when these were both possible
and appropriate. |
| Because The Cochrane
Library is updated and amended as new evidence becomes
available and errors are identified, electronic media
offer obvious advantages for disseminating and
interrogating its contents. The Cochrane Library is
being distributed on disk, the Internet and on CD-ROM,
and there are plans to distribute smaller, specialized
databases derived from the main database as well. |
| |
Comments and Criticisms |
| It is important to make
efficient arrangements for criticising the reviews
prepared by contributors to the Cochrane Collaboration,
and for amending reviews in the light of valid
criticisms. At present, opportunities for criticising
reviews before they are published in print are restricted
by the number and competence of the referees selected by
editors. After a review has been printed, opportunities
for published criticism are usually limited to the few
letters that editors can accept for publication, which
are often unhelpfully brief and non-specific. It is also
frustrating that there is no straight forward way in
which the authors of printed reviews can amend their
reports after taking account of valid criticisms. |
| The quality of
Cochrane reviews is being enhanced by means of an
iterative system through which successive versions of
each review will reflect not only the emergence of new
data, but also valid criticisms, solicited or
unsolicited, from whatever source. Successive versions of
a particular review, together with any intervening
criticisms, will be archived electronically. |
| |
The Cochrane Controlled Trials Register (CCTR) |
| CCTR is a bibliographic
database of controlled trials identified by contributors
to the Cochrane Collaboration and others, as part of an
international effort to systematically search the
world’s health care journals and other sources of
information, and create an unbiased source of data for
systematic reviews. The Cochrane Collaboration embarked
on this formidable task, in co-operation with the
National Library of Medicine in Washington, DC, USA (who
produce Medline), and Reed Elsevier, Amsterdam, The
Netherlands (who produce Embase), because it has been
shown that existing bibliographic databases are
inadequate for the identification of all relevant studies
(Dickersin, 1994). |
| |
Good decisions about health care |
| Good decisions about
health care rely on more than good reviews of the results
of research. The Cochrane Collaboration will make the
results of research assessing the effects of health care
more easily available. However, as Cochrane made
clear in ‘Effectiveness and Efficiency’
(Cochrane, 1972), reliable evidence about the effects of
specific elements of health care, although essential for
improving decisions about health care and research, is
only part of what is needed for better decision making. |
| If better decisions are
to lead to improved health, then effective mechanisms are
needed for implementing them efficiently. Forms of care
that have been shown to do more good than harm should be
encouraged, while those that do more harm than good need
to be discarded. The many forms of care which have
unknown effects should, as far as possible, be used in
the context of a research programme to find out whether
they help or do harm. |
In addition, if people
are to receive care which is appropriate, then policy
makers and decision makers - ranging from ministers of
health to individual clinicians and patients - must
consider people’s needs, the availability of
resources, and priorities.
In making decisions about
the care of individual patients, for example, the results
of the reviews must be integrated with the
clinician’s expertise, which has been acquired
through experience and practice. The results of the
reviews must also be integrated with the patient’s
expertise, which derives from their knowledge of their
condition (particularly if it is a chronic or recurrent
health problem), the treatments on offer, and the
responsiveness or otherwise of the former to the latter. |
| If operating in
synchrony, these complementary forms of expertise are
reflected in more efficient diagnosis and in more
thoughtful identification and compassionate use of the
predicaments, rights, and preferences of individual
patients in making decisions about their care. |
| Similar qualifications
are appropriate when considering the relevance of
Cochrane reviews in decisions taken in respect of whole
communities. The findings in a systematic review of
research evidence may, very rarely, appear to have
universally relevant implications. Usually, however,
universal guidelines and prescriptions for the precise
application of the evidence are neither wise nor
workable. Local disease burdens and barriers to
implementation vary widely from country to country and
from place to place within countries, and local attention
to these issues will help to ensure that the evidence
will help those who can best benefit from it. |
| |
Strategic alliances and the future |
| Many of the achievements
of the Cochrane Collaboration reflect the goodwill and
efforts of the individuals who have contributed and
continue to contribute their time and efforts to the
Collaboration’s activities. |
| Many of these
contributions have been made by individuals who have
received no specific funding support, and the level of
support received by others has varied widely between
countries and agencies. This variation in institutional
support does not alter the fact that the organizations
which have provided resources for the
Collaboration’s activities have also contributed
importantly to its success. To date, these organizations
have tended to be public institutions, such as government
agencies and universities; but there is considerable
scope for non-profit private research funding
organizations and industry to support the
Collaboration’s work. There is a particular
role for the latter, for example, in the development of
more complete registers of the controlled trials which
should be considered for inclusion in Cochrane reviews.
Part of the work done to create such registers has been
funded by the European Union’s Biomed 1 programme
(McDonald, 1996). |
| Within the Cochrane
Collaboration an elected steering group governs the
conduct and evolution of the Collaboration. At a meeting
held in August 1996, the steering group drafted a
strategic plan for the development of the
Collaboration. Four goals were identified towards
which the Collaboration needs to strive: |
| a) to ensure that high
quality systematic reviews are available across a broad
range of health care topics; |
| b) to maximise access to
these systematic reviews; |
| c) to achieve financial
sustainability; and |
| d) to develop an
efficient and transparent organizational structure and
management. |
| A key feature of the
Collaboration’s strategy is to develop appropriate
alliances at local, national and global levels.There are
already many encouraging examples of alliances that
have been formed between the Collaboration and others.
These range from links between some of the collaborative
review groups and local community groups who assist in
the various steps that lead to the preparation of
reliable and relevant systematic reviews about the
effects of health care, through to links at a national
level between individual Cochrane centres and clinical
guideline development programmes. In a project funded by
the European Union’s Biomed 2 programme, in close
co-operation with the Cochrane centres in Australia and
Canada, it has become possible to collaborate on
translating Cochrane materials into languages other than
English, to train trainers for Cochrane reviewers, and to
help establish new review groups and Cochrane centres. At
a global level, the Collaboration has begun to explore
the development of strategic alliances with international
organizations with an interest in health care, with
industry, and with international professional and
consumer organizations. |
| The Collaboration is
still very young but it has already achieved a great deal
(Chalmers, 1997). The continued enthusiasm and goodwill
of individuals, combined with strategic alliances
developed within the context of the Collaboration’s
eight guiding principles, will ensure that it succeeds in
getting to grips with the important agenda bequeathed by
Archie Cochrane. Em
suma, utilizar ou fazer revisões sistemáticas da
literatura é atuar sintetizando informações
adequadas, definindo evidências que validam as
intervenções que usamos no dia-a-dia. E atualmente, é
considerada a forma de evidência mais confiável para
tomada de decisões em saúde (Sackett, 1997). |
| |
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