Frequently Asked Questions - General
The Cochrane Collaboration is named in honour of a British health
care researcher called Archie Cochrane who died in 1988. Information about Archie Cochrane is available here.
A protocol is a plan or set of steps to be followed in a study. A protocol for a systematic review should describe the rationale for the review; the objectives; and the methods that will be used to locate, select and critically appraise studies, and to collect and analyse data from the included studies. (Definition taken from the Glossary to the Cochrane Reviewers' Handbook.)
A review of a clearly formulated question that uses systematic and explicit methods to identify, select and critically appraise relevant research, and to collect and analyse data from the studies that are included in the review. Statistical methods (meta-analysis) may or may not be used to analyse and summarise the results of the included studies. A Cochrane Review is a systematic, up-to-date summary of reliable evidence of the benefits and risks of health care. Cochrane Reviews are intended to help people make practical decisions. For a review to be called a "Cochrane Review" it must be in the Parent Database maintained by The Cochrane Collaboration. The Parent Database is composed of modules of reviews submitted by Collaborative Review Groups (CRG's) registered with The Cochrane Collaboration. The reviews contributed to one of the modules making up the Parent Database are refereed by the editorial team of the CRG, as described in the CRG module. Reviewers adhere to guidelines published in the Cochrane Handbook. The specific methods used in a Review are described in the text of the review. Cochrane Reviews are prepared using Review Manager software provided by the Collaboration and adhere to a structured format that is described in The Cochrane Reviewers' Handbook. (Definition taken from the Glossary to the Cochrane Reviewers' Handbook.)
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The Cochrane Collaboration has not actually conducted research to determine this estimate; it is possible that the estimate of 10-35% comes from the following passage in a chapter by Kerr L White entitled 'Archie Cochrane's legacy: an American perspective' in the book 'Non-random Reflections on Health Services Research: on the 25th anniversary of Archie Cochrane's Effectiveness and Efficiency'. This book (published by the BMJ Publishing Group) was edited by Alan Maynard and Iain Chalmers. Iain was formerly Director of the UK Cochrane Centre, and the driving force behind the establishment of The Cochrane Collaboration; he knew Archie Cochrane well. The passage reads as follows:
"In 1976 Archie [Cochrane] and I [Kerr White] were guests at several institutions in New Zealand and on one occasion we both addressed a meeting at Wellington Hospital. Not wishing to startle unduly the staid group of white coated clinicians I tempered my message slightly by stating, instead of 10-15%, that only between 15-20% of physicians' interventions were supported by objective evidence that they did more good than harm. In mid-sentence Archie suddenly called out: "Kerr, you're a damned liar, you know perfectly well that it isn't more than 10%!" We were probably both correct and may well have used the same study for our observations (funded, I believe, by Gordon McLachlan and the NPHT [Nuffield Provincial Hospitals Trust]. My figures came from a two week survey in 1963 of 19 general practitioners "representing almost every partnership and practice in a northern (British) industrial town". All recorded the "intent" of each prescription written. Those for proprietary drugs with "specific" benefit were 9.3%. Another 22.8% were considered to be of "probable" benefit, 27.2% of "possible" benefit, 28.2% were "hopeful", and 8.9% were regarded as a placebo; 3.6% were
"not stated". Distributions for non-proprietary drugs were similar. (6)
6. Forsyth G. An enquiry into the drug bill. Med Care 1963;1:10-16.
The following three abstracts from the Cochrane Methodology Register, which is part of The Cochrane Library (www.thecochranelibrary.com), contain more recent estimates:
Abeni D, Girardelli CR, Masini C, Aprea R, Melchi CF, Puddu P, Pasquini P. What proportion of dermatological patients receive evidence-based treatment? Archives of Dermatology 2001; 137(6): 771-776
OBJECTIVE: To determine the proportion of dermatological patients who are offered evidence-based therapy in the routine dermatological practice.
METHODS: For every patient seen for the first time at one of our tertiary hospital setting clinics between April and May 1999, the primary diagnosis and the primary intervention were recorded. For each primary diagnosis-primary intervention combination, evidence was searched for in electronic databases from January 1966 to December 1999. The proportion of patients who were offered evidence-based interventions was calculated as the main outcome measure.
RESULTS: With a study sample of 136 patients, 61 different diagnosis-treatment couples were generated and 94 queries on electronic databases were performed (to account for "primary interventions" including more than 1 drug or treatment modality). Eighty-seven (64%) of 136 patients received evidence-based interventions. Evidence from randomized controlled trials was found for 69 patients (50.7% of the sample). Controlled studies lacking randomization or double blinding or including fewer than 20 patients per treatment group dealt with treatments offered to 14 patients (10.3%). The treatments offered to 4 patients (2.9%) were judged to have self-evident validity (ie, trials unanimously judged unnecessary). Symptomatic and supportive measures accounted for most interventions lacking substantial evidence (36% of the patients), but we had to include in this class other important treatment regimens, mainly for rare conditions.
CONCLUSIONS: Most of the study patients received evidence-based care. However, published trials should be carefully appraised, and relevance of clinical end points should be evaluated together with methodological issues. More accessible, clinically oriented, evidence-based information sources are needed.
Baraldini V, Spitz L, Pierro A. Evidence-based operations in paediatric surgery. Pediatric Surgery International 1998; 13: 331-335
It has been assumed that only 10% of medical interventions are supported by solid scientific evidence. The aim of this study was to determine the type of research evidence supporting operations in a tertiary referral paediatric surgical unit. All patients admitted over a 4-week period to two surgical firms were enrolled in the study. All major operations carried out on each patient since birth were evaluated. Patients for whom a diagnosis was not reached were excluded. A bibliographic database (MEDLINE) was used to search for the articles published between January 1986 and December 1995 on the analysed operations. The type of evidence supporting the operations was classified as follows: I=evidence from randomised controlled trials (RCTs); II=self-evident intervention (obvious effectiveness not requiring RCTs); III=evidence from prospective and/or comparative studies; IV=evidence from follow-up studies and/or retrospective case series; and V=intervention without substantial evidence for or against results of randomised trials. Seventy operations (32 individual types) were performed on 49 patients (1-5 operations/patient); 18 (26%) were supported by RCTs (type of evidence I). Two patients (3%) received a self-evident intervention (type II); 48 operations (68%) were based on non-randomised prospective or retrospective studies (type III=13%; type IV=55%). Two patients (3%) received an operation not supported by or against convincing scientific evidence (type V). A significant proportion of operations in paediatric surgery is supported by RCTs. However, the vast majority of these trials were conducted on adult patients. Sixty-eight per cent of the operations were based on prospective follow-up studies or retrospective case series, which may not represent solid scientific evidence. More RCTs are needed in paediatric surgery.
Ellis J, Mulligan I, Rowe J, Sackett DL. Inpatient general medicine is
evidence based. Lancet 1995;346: 407-410.
For many years clinicians have had to cope with the accusation that only 10-20% of the treatments they provide have any scientific foundation. Their interventions, in other words, are seldom "evidence based". Is the profession guilty as charged? In April, 1995, a general medical team at a university-affiliated district hospital in Oxford, UK, studied the treatments given to all 109 patients managed during that month on whom a diagnosis had been reached. Medical sources (including databases) were then searched for randomised controlled trial (RCT) evidence that the treatments were effective. The 109 primary treatments were then classified: 82% were evidence based (ie, there was RCT support [53%] or unanimity on the team about the existence of convincing non-experimental evidence [29%]). This study, which needs to be repeated in other clinical settings and for other disciplines, suggests that earlier pessimism over the extent to which evidence-based medicine is already practised is misplaced.
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This is contained in The Cochrane Manual.
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