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1、Systematic Reviews & Meta-Analysis,An Overview,What is a Systematic Review?,“A review that is conducted according to clearly stated, scientific research methods, and is designed to minimize biases and err
2、ors inherent to traditional, narrative reviews.” Margaliot, Zvi, Kevin C. Chung. Systematic Reviews: A Primer for Plastic Surgery Research. PRS Journal. 120/7 (2007),What is the significance of Systematic Reviews?
3、,The large amount of medical literature requires clinicians and researchers alike to rely on systematic reviews in order to make an informed decision.Systematic Reviews minimize bias. “A systematic review is a more sci
4、entific method of summarizing literature because specific protocols are used to determine which studies will be included in the review.” Kevin C. Chung, MD, Patricia B. Burns, MPH, H. Myra Kim, ScD, “Clinical Perspecti
5、ve: A Practical Guide to Meta-Analysis.” The Journal of Hand Surgery. Vol. 31A No.10 December 2006. p.1671,Why are Systematic Reviews Necessary?,“The volume of published material makes it impractical for an individual c
6、linician to remain up to date on a variety of common conditions. This is further complicated when individual studies report conflicting conclusions, a problem that is prevalent when small patient samples and retrospectiv
7、e designs are used.” Margaliot, Zvi, Kevin C. Chung. “Systematic Reviews: A Primer for Plastic Surgery Research”. PRS Journal. 120/7 (2007) p.1834,Key Characteristics of Systematic Reviews,Clearly stated title a
8、nd objectives Comprehensive strategy to search for relevant studies (unpublished and published)Explicit and justified criteria for the inclusion or exclusion of any studyClear presentation of characteristics of each s
9、tudy included and an analysis of methodological qualityComprehensive list of all studies excluded and justification for exclusion Linda N. Meurer, MD, MPH Department of Family and Community Medicine. “S
10、ystematic Synthesis of the Literature: Introduction to Meta-analysis”. Power Point Presentation.,Characteristics of Systematic Reviews (cont.),Clear analysis of the results of the eligible studiesstatistical synthesis o
11、f data (meta-analysis) if appropriate and possible; or qualitative synthesisStructured report of the review clearly stating the aims, describing the methods and materials and reporting the results Linda N. Me
12、urer, MD, MPH Department of Family and Community Medicine. “Systematic Synthesis of the Literature: Introduction to Meta-analysis”. Power Point Presentation.,An author of a good Systematic Review…,Formulates a QuestionC
13、onducts a Literature SearchRefines the search by applying predetermined inclusion and exclusion criteriaExtracts the appropriate data and assess their quality and validitySynthesizes, interprets, and reports data,Hypo
14、thesis,“A systematic review should be based on principles of hypothesis testing, and the hypotheses must be conceived a priori.” Margaliot, Zvi, Kevin C. Chung. Systematic Reviews: A Primer for Plastic Surgery R
15、esearch. PRS Journal. 120/7 (2007) p. 1836,Focus of the Question,The structured question will determine the inclusion and exclusion criteria:What is the population of interest?What are the interventions?What are the o
16、utcomes of interest?What study designs are appropriate?,Inclusion/Exclusion Criteria,“Once the study question is formalized, the authors must compose a comprehensive list of inclusion and exclusion criteria.”“To avoid
17、selection bias, inclusion and exclusion criteria should be agreed upon and formalized before data extraction and analysis.” Margaliot, Zvi, Kevin C. Chung. “Systematic Reviews: A Primer for Plastic Surgery Rese
18、arch.” PRS Journal. 120/7 (2007) p.1836,Literature Search,“A comprehensive and reproducible literature search is the foundation of a systematic review.” Margaliot, Zvi, Kevin C. Chung. “Systematic Reviews: A Pr
19、imer for Plastic Surgery Research.” PRS Journal. 120/7 (2007) p.1837,Literature Search Challenges,Database Bias - “No single database is likely to contain all published studies on a given subject.”Publication Bias - sel
20、ective publication of articles that show positive treatment of effects and statistical significance.Hence, it is important to search for unpublished studies through a manual search of conference proceedings, corresponde
21、nce with experts, and a search of clinical trials registries. Margaliot, Zvi, Kevin C. Chung. “Systematic Reviews: A Primer for Plastic Surgery Research.” PRS Journal. 120/7 (2007) p.1837,Literature Review Chall
22、enges (cont.),English-language bias - occurs when reviewers exclude papers published in languages other than EnglishCitation bias - occurs when studies with significant or positive results are referenced in other public
23、ations, compared with studies with inconclusive or negative findings,Data Collection,“The list of data to be extracted should be agreed upon a priori consensus during the design stage of the study.” Margaliot, Z
24、vi, Kevin C. Chung. “Systematic Reviews: A Primer for Plastic Surgery Research.” PRS Journal. 120/7 (2007) p.1839,Data Collection (cont.),Collected data includes:Study characteristicsSample demographicsOutcome data,Da
25、ta Collection (cont.),“It is necessary to design a review-specific data extraction form, so that the same data are extracted from each study and missing data are clearly apparent.” Margaliot, Zvi, Kevin C. Chung
26、. “Systematic Reviews: A Primer for Plastic Surgery Research.” PRS Journal. 120/7 (2007) p.1839,Data Collection (cont.),“To ensure that data extraction is accurate and reproducible, it should be performed by at least two
27、 independent readers.” Margaliot, Zvi, Kevin C. Chung. “Systematic Reviews: A Primer for Plastic Surgery Research.” PRS Journal. 120/7 (2007) p.1839,Quality Assessment,“The validity of a systematic review ultima
28、tely depends on the scientific method of the retrieved studies and the reporting of data.” Margaliot, Zvi, Kevin C. Chung. “Systematic Reviews: A Primer for Plastic Surgery Research.” PRS Journal. 120/7 (2007) p
29、.1839,Quality Assessment (cont.),Randomized Controlled Trials (RCT):RCT are considered to be more rigorous than observational studiesA review based on well-designed RCT will likely be more valid and accurate than a rev
30、iew based on observational studies or case reports Margaliot, Zvi, Kevin C. Chung. “Systematic Reviews: A Primer for Plastic Surgery Research.” PRS Journal. 120/7 (2007) p.1839,Quality Assessment (cont.),“The mo
31、st common way to assess and report study quality has been using a composite, numerical scoring instrument.” Margaliot, Zvi, Kevin C. Chung. “Systematic Reviews: A Primer for Plastic Surgery Research.” PRS Journ
32、al. 120/7 (2007) p.1839,Quality Assessment (cont.),“More than 35 different quality assessment instruments have been published in the literature, and most are designed for randomized clinical trials.” Margaliot,
33、Zvi, Kevin C. Chung. “Systematic Reviews: A Primer for Plastic Surgery Research.” PRS Journal. 120/7 (2007) p.1839,Jadad score & Chalmers score,“The Jadad score and the T.C. Chalmers score are two examples of quality
34、 assessment instruments.” Margaliot, Zvi, Kevin C. Chung. “Systematic Reviews: A Primer for Plastic Surgery Research.” PRS Journal. 120/7 (2007) p.1839,Jadad score,Randomization (2 points possible)1 point if
35、study described as randomizedAdd 1 point if randomization method described and appropriate (e.g. random numbers generated) Deduct 1 point randomization described and inappropriateDouble-blinding (2 points possible)1
36、 point if study described as double-blindedAdd 1 point if method of double-blinding described and appropriate Deduct 1 point if double-blinding described and inappropriateWithdrawals (1 point possible)Give 1 point f
37、or a description of withdrawals and drop-outs Linda N. Meurer, MD, MPH Department of Family and Community Medicine. “Systematic Synthesis of the Literature: Introduction to Meta-analysis”. Power Point Presentat
38、ion.,Jadad Score Example,Data Synthesis,“Once the data have been extracted and their quality and validity assessed, the outcomes of individual studies within a systematic review may be pooled and presented as summary out
39、come or effect” Margaliot, Zvi, Kevin C. Chung. “Systematic Reviews: A Primer for Plastic Surgery Research.” PRS Journal. 120/7 (2007) p.1840,Data Synthesis (cont.),The authors summarize heterogeneous data qual
40、itatively“Data that are very conflicting and widely variable should not, under most circumstances, be combined numerically.” Margaliot, Zvi, Kevin C. Chung. “Systematic Reviews: A Primer for Plastic Surgery Res
41、earch.” PRS Journal. 120/7 (2007) p.1840,When can data in a systematic review be synthesized numerically?,When data are NOT too sparse, of too low quality or too heterogeneous For example: the patients, interventions an
42、d outcomes in each of the included studies are sufficiently similar,Meta-Analysis,“Meta-analysis is a statistical technique for combining the results of independent, but similar, studies to obtain an overall estimate of
43、treatment effect.” Margaliot, Zvi, Kevin C. Chung. “Systematic Reviews: A Primer for Plastic Surgery Research.” PRS Journal. 120/7 (2007) p.1840,Meta-Analysis (cont.),“While all meta-analyses are based on syste
44、matic review of literature, not all systematic reviews necessarily include meta-analysis.” Margaliot, Zvi, Kevin C. Chung. “Systematic Reviews: A Primer for Plastic Surgery Research.” PRS Journal. 120/7 (2007)
45、p.1840,Meta-Analysis(cont.),“If a meta-analysis is to be included in a systematic review, an experienced statistician or an epidemiologist should be consulted during all phases of the study.” Margaliot, Zvi, Ke
46、vin C. Chung. “Systematic Reviews: A Primer for Plastic Surgery Research.” PRS Journal. 120/7 (2007) p.1840,Meta-analysis (cont.),“Protocols for the reporting of meta-analysis results were developed for RCTs (Quality of
47、Reports of Meta-analysis [QUOROM] and Observational Studies in Epidemiology [MOOSE].” Kevin C. Chung, MD, Patricia B. Burns, MPH, H. Myra Kim, ScD. “Clinical Perspective: A Practical Guide to Meta-Analysis.” Th
48、e Journal of Hand Surgery. Vol.31A No.10 December 2006. p. 1672,Protocols,The purpose of QUOROM and MOOSE guidelines is to provide proper procedures for conducting a meta-analysis and to standardize the methods of repo
49、rting a meta-analysis. Kevin C. Chung, MD, Patricia B. Burns, MPH, H. Myra Kim, ScD. “Clinical Perspective: A Practical Guide to Meta-Analysis.” The Journal of Hand Surgery. Vol.31A No.10 December 2006. p. 167
50、2,Steps of Meta-analysis,Define the Research QuestionPerform the literature searchSelect the studiesExtract the dataAnalyze the dataReport the results,Meta-analysis: The Research Question,“Common questions addressed
51、 in meta-analysis are whether one treatment is more effective than another or if exposure to a certain agent will result in disease.” Kevin C. Chung, MD, Patricia B. Burns, MPH, H. Myra Kim, ScD. “Clinical Persp
52、ective: A Practical Guide to Meta-Analysis.” The Journal of Hand Surgery. Vol.31A No.10 December 2006. p. 1672,Meta-analysis: Performing the Literature Search,“The literature search is a critical step in the meta-analy
53、sis and often the most difficult part.” Kevin C. Chung, MD, Patricia B. Burns, MPH, H. Myra Kim, ScD. “Clinical Perspective: A Practical Guide to Meta-Analysis.” The Journal of Hand Surgery. Vol.31A No.10 Dec
54、ember 2006. p. 1672,Meta-analysis: The Literature Search (cont.),“The researcher should search more than just MEDLINE to ensure a comprehensive search.” Kevin C. Chung, MD, Patricia B. Burns, MPH, H. Myra Kim,
55、ScD. “Clinical Perspective: A Practical Guide to Meta-Analysis.” The Journal of Hand Surgery. Vol.31A No.10 December 2006. p. 1673,Meta-analysis:The Literature Search (cont.),Search for published studies in MEDLINE, EM
56、BASE, and CINAHL.Search for unpublished clinical trials in the Cochrane Central Register of Controlled Trials,Meta-analysis: Study Selection,“The inclusion and exclusion criteria for studies needs to be defined at the b
57、eginning, during the design stage of the meta-analysis.”“Factors determining inclusion in the analysis are study design, population characteristics, type of treatment or exposure, and outcome measures.” Kevin
58、C. Chung, MD, Patricia B. Burns, MPH, H. Myra Kim, ScD. “Clinical Perspective: A Practical Guide to Meta-Analysis.” The Journal of Hand Surgery. Vol.31A No.10 December 2006. p. 1673,Meta-analysis: Study Selection (cont
59、.),Meta-analysis needs to be documented“One should keep track of the studies included and excluded at each step of the selection process to document the selection process.” Kevin C. Chung, MD, Patricia B. Burn
60、s, MPH, H. Myra Kim, ScD. “Clinical Perspective: A Practical Guide to Meta-Analysis.” The Journal of Hand Surgery. Vol.31A No.10 December 2006. p. 1673,Meta-analysis: Study Selection (cont.),“The QUOROM guidelines for
61、reporting a meta-analysis requests that investigators provide a flow diagram of the selection process.” Kevin C. Chung, MD, Patricia B. Burns, MPH, H. Myra Kim, ScD. “Clinical Perspective: A Practical Guide to
62、Meta-Analysis.” The Journal of Hand Surgery. Vol.31A No.10 December 2006. p. 1673,The Validity of a Meta-analysis,“The validity of a meta-analysis depends on the quality of the studies included, and an assessment of qu
63、ality is a necessary part of the process.” Kevin C. Chung, MD, Patricia B. Burns, MPH, H. Myra Kim, ScD. “Clinical Perspective: A Practical Guide to Meta-Analysis.” The Journal of Hand Surgery. Vol.31A No.10
64、December 2006. p. 1674,Meta-analysis: Extracting the Data,“The type of data to be extracted from each study should be determined in the design phase and a standardized form is constructed to record the data.” K
65、evin C. Chung, MD, Patricia B. Burns, MPH, H. Myra Kim, ScD. “Clinical Perspective: A Practical Guide to Meta-Analysis.” The Journal of Hand Surgery. Vol.31A No.10 December 2006. p. 1674,Meta-analysis: Data,What are th
66、e examples of data commonly extracted?Study design, descriptions of study groups, diagnostic information, treatments, length of follow-up evaluation, and outcome measures.,Meta-analysis: Data,“The difficulty with data e
67、xtraction is that studies often use different outcome metrics, which make combining the data awkward. The data should be converted to a uniform metric for pooling.” Kevin C. Chung, MD, Patricia B. Burns, MPH, H
68、. Myra Kim, ScD. “Clinical Perspective: A Practical Guide to Meta-Analysis.” The Journal of Hand Surgery. Vol.31A No.10 December 2006. p. 1674,Meta-analysis: Analyzing the Data,There are 2 statistical models used in a
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