به نام خداوند بخشنده مهربان. Introduction to Systematic Reviews and Meta-analysis. Dr. Kourosh Sayehmiri

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1 به نام خداوند بخشنده مهربان Introduction to Systematic Reviews and Meta-analysis Dr. Kourosh Sayehmiri

2 رشد مقاالت متاآنالیز در پنج کشور اول خاورمیانه از نظر تعداد مقاله بر اساس جستجویی در مجالت ایندکس شده در مدالین

3 Information about Health Care Is Everywhere But how do you know if one health care intervention works better than another Or if it will do more harm than good?

4 Typical Clinical Questions Are antioxidant supplements effective for preventing mortality in healthy participants? Do annual general health checks (annual physical exams) reduce illness and mortality? Is an early epidural as effective and safe as a late epidural for women in labor?

5 What is a Meta-Analysis? Meta-analysis is the statistical procedure for combining data from multiple studies. Meta-analysis refers to the analysis of analyses When the treatment effect (or effect size such as: correlation coefficients(r) odds-ratios(or) Relative Risk(RR) proportions(p) Mean, Mean difference Risk difference

6 consistent from one study to the next, meta-analysis can be used to identify this common effect. When the effect varies from one study to the next, meta-analysis may be used to identify the reason for the variation.

7 Why do a Meta-Analysis? Decisions about the utility of an intervention or the validity of a hypothesis cannot be based on the results of a single study, because results typically vary from one study to the next. Rather, a mechanism is needed to synthesize data across studies. Narrative reviews had been used for this purpose, but the narrative review is largely subjective (different experts can come to different conclusions)

8 and becomes impossibly difficult when there are more than a few studies involved.

9 Traditional Narrative Reviews No standard format No clearly specified methods of identifying, selecting, and validating included information Quantitative synthesis rarely used to integrate the information from multiple studies

10 Meta-analysis, by contrast, applies objective formulas (much as one would apply statistics to data within a single study), and can be used with any number of studies. Meta-analysis gives more weight to studies with more precise estimates.

11 Aims هدف از متاآناليز 1. Increases the statistical power of a comparison 2. Improves the estimation of the effect of a treatment 3. Combines the results of studies that are contrasting 4. Answers new questions 5. Analysis sub-groups of subjects selected from different studies 6. Analysis trends (e.g within a time- frame ) 7. Defines areas in which further studies are needed 8. It is always possible to update a meta-analysis if it is not conclusive.

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17 When Can You Do Meta-analysis? Meta-analysis is applicable to collections of research that: Are empirical, rather than theoretical Produce quantitative results, rather than qualitative findings Examine the same constructs and relationships Have findings that can be configured in a comparable statistical form (e.g., as effect sizes, correlation coefficients, odds-ratios, proportions)

18 Importance of meta-analysis in evidence-based medicine(ebm) Meta-analysis RCT Before-after clinical trials Cohort Studies Case-control Studies Cross-sectional Studies Case series Studies Case Report Studies

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21 Timely response A classic example: streptokinase in myocardial infarction First trial published in trials published up to 1977 Introduced as normal practice in late 80s Meta-analysis of treatments in 1992: fall in mortality by 1977, after inclusion of 15 trials

22 Routine Specific Rare/Never Experimental Not Mentioned Cumulative Year RCTs Pts Thrombolytic Therapy Textbook/Review Recommendations P< P<.001 P< Odds Ratio (Log Scale) M M M M M M Favours Treatment Favours Control

23 ریسک اسکیزوفرنی در ارتباط با پلی مورفیسم Val66Metژن ( BDNFفاکتور نورونی مشتق شده مغزی(: یک مطالعه مرور سیستماتیک و متاآنالیز مطالعات مورد شاهدی

24 Television viewing and risk of type 2 diabetes, cardiovascular disease, and all-cause mortality: a meta- analysis. JAMA JUN 2011 CONCLUSION: Prolonged TV viewing was associated with increased risk of type 2 diabetes, cardiovascular disease, and all-cause mortality

25 Risk of incident diabetes with intensive-dose compared with moderate-dose statin therapy: a metaanalysis. JAMA 2011 CONCLUSION: In a pooled analysis of data from 5 statin trials, intensive-dose statin therapy was associated with an increased risk of new-onset diabetes compared with moderate-dose statin therapy.

26 Prevalence and trend of hepatitis C virus infection among blood donors in Iran: A systematic review and meta-analysis Mazaher Khodabandehloo, Daem Roshani, Kourosh Sayehmiri

27 When Not to Do a Metaanalysis? Garbage in garbage out A meta-analysis is only as good as the studies in it Narrower confidence interval around combination of biased studies worse than the biased studies on their own Beware of reporting biases Mixing apples with oranges Not useful for learning about apples, although useful for learning about fruit! Studies must address the same question

28 How Do You Do a Systematic Review and meta-analysis? Step 1: gather together your team Step 2: develop your protocol Step 3: data collection: locate, screen, and collect studies Step 4: abstract data and appraise risk of bias in the individual studies Step 5: synthesize findings, interpret, and assess overall body of evidence Step 6: write report Step 7: update

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