Ressurser for oversiktsforfattere

Deltakelse i Cochrane-samarbeidet som oversiktsforfatter: Du kan melde deg inn i den oversiktsgruppen som er mest relevant i forhold til ditt helsefaglige interesseområde. Hvis du ikke finner en gruppe som ser relevant ut, registrer deg som interessert i å delta i en ny gruppe. Som medlem av en oversiktsgruppe får du støtte og opplæring i arbeidet med en systematisk oversikt, og et internasjonalt publikum når arbeidet ditt publisr i The Cochrane Library.

 

• Cochrane Handbook for Systematic Reviews of Interventions - offisiell håndbok for utarbeiding av Cochrane-oversikter
• RevMan homepage - dokumentasjon og veiledning for programvaren som benyttes for å lage og oppdatere Cochrane-oversikter.
• Cochrane Style Resource – sjekk din Cochrane-oversikt opp mot de offisielle språklige retningslinjene
• Using Individual Patient Data - Power Point-presentasjon
• Browse the list of Cochrane Review Groups
• Re-publishing of reviews - forklaring av prosedyrer og søknadsskjema for å få tillatelse til å publisere din Cochrane-oversikt I et annet vitenskapelig tidsskrift QUOROM statement checklist (PDF-dokument). Sjekkliste over ting som oversiktsforfattere kan framheve I oversikten for å forsikre leserne om påliteligheten av funnene.

Opplæring ansikt til ansikt

Kontakt Cochrane-senter eller oversiktsgrupper for informasjon om lokale workshops og kurs I hvordan lage systematiske oversikter. Noen av disse er omtalt på ”the Cochrane workshops”-siden.

Nettbasert opplæring

Open Learning Materials – lær framgangsmåten I passe store, nettbaserte moduler Dette er et supplement til Cochrane Reviewers' Handbook – til hjelp I prosessen med å ferdigstille en oversikt.

Opplæringstilbud fra andre organisasjoner:

Undertaking Systematic Reviews of Research on Effectiveness – omfattende veileder fra NHS Centre for Reviews & Dissemination  

 

Methods used in reviews

Search strategies

Access to specialised register by reviewers

Once a protocol has been accepted for publication, the Review Group Co-ordinator (RGC) provides the review authors with a list of potential trial references identified from the PVD Group's Specialised Register and from searching the most recent issue of The Cochrane Library. Review authors do not have direct access to the Specialised Register except via The Cochrane Central Register of Controlled Trials (CENTRAL), in The Cochrane Library. These lists are updated every three months until a draft review is received. Annual lists are sent to authors of published reviews.

Additional search strategies

Authors are encouraged to search electronic databases, specialised journals, conference proceedings, the reference lists in trial reports and in other published reviews relevant to their topic area, and the Science Citation Index to identify articles that have cited the studies included in the review. Authors are also encouraged to contact pharmaceutical companies to obtain data on unpublished studies.

Study selection

Two guides, addressing venous and arterial disease, have been produced by the PVD Group to assist authors to decide upon appropriate outcomes for inclusion in reviews.

The PVD Group recommends that authors restrict their reviews to randomised controlled trials. For some interventions, only quasi-randomised or controlled clinical trials may be available. Selection of studies for inclusion in reviews should be done independently by more than one review author. Disagreements should be resolved by discussion and where possible, by a third author.

Assessment of methodological quality

The PVD Group recommends that assessment of trial quality should done independently by more than one review author. Disagreements should be resolved by discussion and where necessary, by a third author. Authors of reviews are referred to Section 6.0 of the Cochrane Handbook for Systematic Reviews of Interventions 4.2.6 (updated September 2006) for more detailed information. Quality assessment checklists are provided by the PVD Group.

Adequacy of the randomisation process:
A - Adequate sequence generation is reported for example, using random number tables, computer random number generator, coin tossing or card shuffling.
B -  did not specify on the adequate reported methods in (A) but mentioned randomisation method.
C - Other method of allocation that may not be random.

Adequacy of allocation concealment:                                                                                                                         A - Adequate: allocation concealment described that would not allow investigators /participants to know or influence intervention group before eligible participant entered in the study, for example central randomisation, serially numbered, opaque, sealed envelopes.
B - Unclear: unclearly concealed trials in which the author either did not report allocation concealment approach at all, or reported an approach that was not clearly adequate.
C - Inadequate: inadequately concealed trials in which the method of allocation  is not concealed, such as alternation methods or unsealed envelopes; any information in the study that indicated that investigators or participants could influence intervention group.

Blinding:                                                                                                                                                                               A - Blinding of treatment providers: Yes/No/Unclear.
B - Blinding of participants: Yes/No/Unclear.
C - Blinding of outcome assessor: Yes/No/Unclear.
D - Blinding of data analysis: Yes/No/Unclear.

Intention-to-treat analysis (ITT)                                                                                                                                   A - Yes: Specifically reported by authors that ITT was undertaken and this was confirmed on study assessment, or not stated but evident form study assessment that ITT was undertaken.
B - Unclear: Described as ITT analysis but unable to confirm on study assessment, or not reported and unable to confirm by study assessment.
C - No: Lack of ITT analysis confirmed on study assessment, for example patients who were randomised were not included in the analysis because they did not receive the study intervention, or they withdrew from the study, or were not included because of protocol violation, regardless of whether ITT reported or not.

Completeness of follow up:                                                                                                                             Percentage of participants for whom data was completed at defined study end-point.

Data collection

The PVD Group recommends that data extraction should be done independently by more than one review author. Disagreements should be resolved by discussion and where necessary, by a third author. Further information should be sought from the authors of published trials. Unpublished data should always be identified as such and its source acknowledged.

Analysis

Authors of reviews are referred to Section 9.0 of the Cochrane Handbook for Systematic Reviews of Interventions Version 5.0.0 [updated February 2008] for information on analysing and presenting results in reviews. Data should be entered into RevMan 5.0 by at least two authors using the double data entry function.

Prior to publication all reviews are examined by a statistician for suitability of statistical techniques applied to the data. A summary of the statistical guidelines is given below:

Summary statistics: dichotomous outcomes (Handbook Section 9.2.1)
The PVD Group recommends calculation of the relative risks (risk ratios) because of their ease of interpretation. However, in some circumstances there may be good reasons for preferring a different statistic, e.g. the Peto odds ratio appears to perform best when data are very sparse.

Summary statistics: continuous outcomes (Handbook Section 9.2.3)
The PVD Group recommends calculation of the mean difference (MD) if the outcomes are measured in a standard way between trials. Standard mean difference (SMD) should be used only when necessary, i.e. when outcomes are conceptually the same but measured in different ways (e.g. pain scores using different scales).

All continuous outcome data require a mean and standard deviation for each group from each trial. Often reports present the standard error of the mean (SEM) rather than the standard deviation. This is much smaller, and will, if used in a meta-analysis, give far too much weight to that study. If one study appears to have a much smaller standard deviation than the others, it may be that the SEM has been erroneously reported as the standard deviation. SEM can be converted to standard deviation by multiplying it by the square root of the sample size. If standard deviations are not reported, it may be possible to calculate them from statistics given in the paper: the Handbook (section 8.5.2) presents methods for doing this.

Fixed-effect model versus random-effects analysis: The choice between fixed and random effects is not straightforward and there is considerable debate among statisticians about when each method is preferable. There is inevitably an element of subjectivity in the choice, but it is important that whatever decision is made can be justified.

Fixed-effect analysis may be used if all of the trials in the analysis are sufficiently similar that it is a reasonable assumption that the underlying effect size is the same for all of them. If this assumption is not reasonable, use random-effects analysis to obtain an overall summary, or do not combine the trials. If hetereogeneity has been detected, it may be inapprorpiate to combine resulst to produce a single summary measure. Results of the chi-squared heterogeneity test should not be used to guide the choice of statistical method.

Subgroup analyses:
It is necessary to keep subgroup analyses to a minimum to avoid generating spurious results. Therefore, each subgroup analysis should have a clear rationale, which should be explained in the background, pre-specified in the protocol, and only these subgroup analyses should be conducted. Subgroup analyses have great potential to be misleading so their results should be interpreted with caution.  

Sensitivity analysis: A minimum set of sensitivity analyses for authors to perform includes repeating the analysis:

1. excluding studies of lower methodological quality;
2. excluding any unpublished studies;
3. excluding very large studies (if present);
4. excluding other types of studies, depending on the degree to which there were choices about the inclusion/exclusion criteria (e.g. with/without trials that had different age groups, different dosages); 5. using the risk difference/odds ratio.

We recommend constructing a funnel plot where a reasonable number of studies have been included in a review, to examine the possibility of publication bias.

Outcomes with no data: Authors are encouraged to include outcomes of interest outlined in the protocol in the analysis even when no data are available.

Reporting of reviews

The Group has no written policy on the reporting of results. Review authors are recommended to follow the guidance given in the Cochrane Handbook for Systematic Reviews of Interventions. Where possible, review authors should comment on the applicability of their findings, and include any information relevant to health-care decision making, such as adverse events and adverse effects, prescribing data and costs.

 

Editorial process

Titles

Potential authors wishing to register a title are required to complete a title registration form (available from the editorial base, the PVD Group website (http://pvd.cochrane.org/en/index.html) and return it to the editorial base for consideration by the editors. Details of the scope of the proposed review, extent and severity of disease, treatment(s) to be reviewed, and treatment(s) against which it will be compared are requested on the title registration form. As well as being sent to the editors for consideration, titles are also broadcast via the Information Managment System to enable other CRGs to register an interest to avoid overlap. Authors are notified within one week of the editors' decision to accept or reject a title. The editors may request the title or scope of a proposed review to be modified before it is accepted.

If more than one person proposes to do the same review the Review Group Co-ordinator (RGC) will attempt to establish a collaboration between the parties, and will arbitrate during disagreements as required. The co-ordinating editor will make the final decision.

Once a title has been registered, the contact author is sent acceptance information about the editorial process, software, information on preparing the protocol, the editorial process and checklists.

Protocols should be delivered to the editorial base within three months of a title being registered. Titles which have been registered for more than twelve months, for which protocols have not been forthcoming, are 'de-registered' and are listed on the PVD Group's website for registration by other group members.

Protocols

The PVD Group encourages authors and co-authors to attend a workshop on, 'Developing a protocol', before commencing work. Protocols are expected to be submitted within three months of title registration.

Draft protocols are sent to a minimum of two editors for comments. Editors are requested to return comments to the editorial base within three weeks. The comments are then forwarded to the review's contact author, and circulated amongst the editors for information. Revised version(s) of the protocol will be sent out to all editors until the protocol is approved for publication.

Authors are aware of the identity and contact details of the editors who comment on their protocols and, in the event of a difference of opinion, are free to engage in discussion with them to establish a solution.

Copy-editing of protocols is done at the editorial base by the RGC and subsequently sent to copy edit support for checking. The Trials Search co-ordinator (TSC) checks all search strategies. Authors are asked to approve the final version prior to publication on CDSR.

Reviews should be submitted within twelve months of the protocol being accepted for publication on CDSR (i.e. fifteen months after registration).

Reviews

Contact authors are sent further information on preparing the review once their protocol has been accepted for publication. Advice on specific problems/queries is available from the editorial base. The RGC searches for potential trials in the Specialised Register and in the most recent issue of The Cochrane Library. The resultant citations from the reference search are added to the 'Classification pending' section of the RevMan file by the RGC and sent to the contact author. This is designed to assist review authors and to reduce errors in reference citations. 

The PVD Group recognises that authors are better equipped to write reviews once they have attended appropriate workshops. The Group has held workshops addressing general and specific problems encountered in the review writing process in association with its annual meetings 1997-2001. Workshops held have included, 'Dealing with continuous data', 'Developing a protocol', 'Getting a review into RevMan' (computer-based workshop), and a new workshop, 'How to prepare a review' (1999 onwards), that follows on from the 'Developing a protocol' workshop. In addition to in-house workshops, the PVD Group has held workshops at specialist conferences and training days within the UK. Authors and contact authors are also encouraged to attend workshops hosted by their nearest Cochrane Centres.

Facilities are available for authors and co-authors to attend the editorial base to work on their reviews.

Draft reviews are sent to a minimum of two editors as well as the statistical editor, and two external referees, one of whom is normally an expert in the field and the other is usually a consumer or 'end-user', for comments. Editors are requested to return comments to the editorial base within three weeks. The comments are then forwarded to the review's contact author, and circulated amongst the editors for information. Revised version(s) of the review will be sent out to all editors until it is approved for publication.

Authors are aware of the identity and contact details of the editors who comment on their reviews and, in the event of a difference of opinion, are free to engage in discussion with them to establish a solution.

Copy-editing of reviews is done at the editorial base by the RGCs and the TSC and then sent to copy edit support for checking. Authors are asked to approve the final version prior to publication on CDSR. It is the PVD Group's policy to send all reviews to the Cochrane Consumer Network for input into the plain language summaries. Authors may draft the plain language summary themselves (ideally with consumer input on content and readability), but the final copy of their review will be sent by the PVD Group to the Cochrane Consumer Network to confirm eligibility.

Updating

The editorial base monitors its Specialised Register for trials identified since reviews were last published, that might be relevant for inclusion in updated reviews. Authors are advised of appropriate trials and are asked to examine reviews on an annual basis with a view to updating them, although the Collaboration now allows two years before updating is required. If no new trials have been identified, and no changes are desired by the editorial base or the author, then the review may be updated as it stands. If changes are required, authors have nine months in which to update the review. Revised reviews are edited by a minimum of two editors and, if necessary, the statistical editor prior to re-publication.

Reviews that include preliminary data from on-going trials are required to take subsequent data into account as soon as possible after publication of the data. Revised reviews will be edited by two editors and, if necessary, the statistical editor.

Authors are aware of the identity and contact details of the editors who comment on their reviews and, in the event of a difference of opinion, are free to engage in discussion with them to establish a solution.

Copy-editing of reviews is done at the editorial base by the RGCs and the TSC and then sent to copy edit support for checking. Authors are asked to approve the final version prior to publication on CDSR.

Feedback (previously 'Comments and Criticisms'): Reviews sometimes need to be updated in the light of comments received through the 'Feedback' facility in The Cochrane Library. Authors are obliged to provide a response to criticism, and, if significant changes are made to a review as a result, the revised review would be subjected to the same editorial requirements as an updated review.