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Systematic review and meta analysis
- 3. What are they? • A systematic review answers a defined research question by collecting and summarizing all empirical evidence that fits pre-specified eligibility criteria. • A meta-analysis is the use of statistical methods to summaries the results of these studies
- 5. Continue A systematic review collects all possible studies related to a given topic and design, and reviews and analyzes their results. During the systematic review process, the quality of studies is evaluated, and a statistical meta-analysis of the study results is conducted on the basis of their quality. A meta-analysis is a valid, objective, and scientific method of analyzing and combining different results.
- 6. Reason to do Meta-analysis When you looked at the individual studies, they may potentially report differing effect from the treatment. "which one do I take". In MA, you bring all different effect together and MA gives you summarized effect from across all these different studies. Each of the study by itself may have small sample size, result may be questionable.
- 7. Continue… Meta-analyses are conducted to assess the strength of evidence present on a disease and treatment. One aim is to determine whether an effect exists; another aim is to determine whether the effect is positive or negative and, ideally, to obtain a single summary estimate of the effect.
- 8. Relationship between SR and MA • SR is the process of undertaking the reviews, and MA may be one outcome. • Not all systematic reviews include meta-analysis, but all meta-analysis are found in systematic reviews.
- 10. Results from Medline search using text "meta-analysis"
- 11. Study planning It is easy to confuse systematic reviews and meta-analyses. A systematic review is an objective, reproducible method to find answers to a certain research question, by collecting all available studies related to that question and reviewing and analyzing their results. A meta-analysis differs from a systematic review in that it uses statistical methods on estimates from two or more different studies to form a pooled estimate. Following a systematic review, if it is not possible to form a pooled estimate, it can be published as is without progressing to a meta-analysis; however, if it is possible to form a pooled estimate from the extracted data, a meta-analysis can be attempted. Systematic reviews and meta-analyses usually proceed according to the flowchart presented in Fig.
- 13. Define Research Question and Review Literature Meta-analyses begin with defining the research question. A defined research question identifies the population affected by the intervention and the potential outcome(s) of treatment. For example, Are men who smoke for 10 or more years at greater risks for lung cancer than men who have never smoke? This question defines the population, and it identifies lung cancer as the outcome of the intervention.
- 14. Literature search Reviewing the literature for studies that answer your research question comes after your question has been defined. • MEDLINE • EMBASE • PUBMED • Cochrane Collaboration • GOOGLE SCHOLORS • Gray literature
- 15. Select Appropriate Studies • Selecting the appropriate studies is probably the most important step of a meta-analysis. papers that are duplicates, that are written in a language you can't understand, or that are not clinical studies, can be eliminated. • After eliminating papers that are clearly not useful, screen the rest of the papers a bit more deeply for eligibility. Several elements can be used to determine a paper's eligibility for the analysis, but it is important that all of the studies you include have the information that you need in order to do your analysis.
- 16. Extract Data The next step in the process is extracting the data for analysis and synthesis. The extracted data depends on the research question, but it may include information such as sample size, patient characteristics, length of study, and a statistical measure, such as confidence interval, odds ratio, risks ratio, mean difference, or hazard ratio.
- 18. Analyze data • Once you have organized it, your next step is to analyze the data using statistical software. A forest plot will allow you to compare statistical differences between groups.
- 19. Dichotomous variables and continuous variables In data analysis, outcome variables can be considered broadly in terms of dichotomous variables and continuous variables. When combining data from continuous variables, the mean difference (MD) and standardized mean difference (SMD) are used (Table 1) MD = mean difference between the mean value in two groups SMD = difference in mean outcome between group standard deviation of outcomeamong participants
- 20. Summary of Meta –analysis Methods available in RevMan Type of data Effect measure Fixed-effect model Random-effect model Dichotomous Odds ratio(OR) Mantel-Haenaszel (M-H) Mantel-Haenaszel (M-H) Inverse variance(IV) Inverse variance(IV) Peto Risk ratio(RR) Mantel-Haenaszel (M-H) Mantel-Haenaszel (M-H) Risk difference (RD) Inverse variance(IV) Inverse variance(IV) Continuous Mean difference (MD),Standardized Difference Mean(SDM) Inverse variance(IV) Inverse variance(IV)
- 23. Forest plot representing homogeneous data
- 24. Publication bias Impact on meta-analysis Meta-analyses and systematic reviews can account for publication bias by including evidence from unpublished studies and the grey literature. The presence of publication bias can also be explored by constructing a funnel plot in which the estimate of the reported effect size is plotted against a measure of precision or sample size.
- 26. MEDCALC Software MedCalc - "MedCalc is a complete statistical program for Windows designed to closely match the requirements of biomedical researchers. It is fast, very user-friendly and reliable”. • more than 220 statistical tests, procedures and graphs • reference software for ROC curve analysis... • method comparison and method evaluation including Bland & Altman plot, Passing & Bablok, and Deming regression, ... • reference intervals • meta-analysis
- 27. Advantages of systematic review • The methods that scientists use to find and select studies reduce bias and are more likely to produce reliable and accurate conclusions. • A review summarizes findings from multiple studies. This makes the information easier for the end user to read and understand. • give an idea of how well findings might apply to everyday practice • reduce bias when drawing conclusions, as it takes in a range of views and findings • Systematic reviews also offer practical advantages. They are less costly to carry out than a new set of experiments, and they take less time. .
- 28. Limitations in Systematic Reviews/Meta- analysis Even though systematic review and meta-analysis are considered the best evidence for getting a definitive answer to a research question, there are certain inherent flaws associated with it, such as the location and selection of studies, heterogeneity, loss of information on important outcomes, inappropriate subgroup analyses and duplication of publication.
- 29. The role of editors and peer reviewers The decisions of journal editors and peer reviewers can also lead to publication bias. Sometimes, results do not reach the publication stage because there is funding for research, but this does not cover the cost of analyzing and publishing the results. This can limit the motivation to write up and submit any negative or neutral findings for publication.
- 30. “If only we knew what we know!” “Anything you can do ………. I can do Meta!”