Research Methods Midterm Flashcards
Systematic Review
- Structured review of primary studies integrating statistical analysis to the results, if appropriate
- Has scientific protocol with objectives and methods
- May include a meta-analysis
Meta-Analysis
Quantitative synthesis of 2 or more studies to produce a single estimate of the effect of an intervention or exposure
Narrative Review
Qualitative, narrative summaries of evidence on a given topic that involves informal and subjective methods to collect and interpret information, and is usually written by experts in the field
Systematic Reviews vs. Narrative Reviews
Narrative reviews are worse because…
-They are subjective (prone to bias and error)
+No description of the methods use by review
+Literature search may be incomplete or selective
+May not be able to distinguish research from opinion
-They are usually not quantitative
+No estimate of overall effects
+Cannot detect small effects
Systematic Review: Reasons to Perform
- Manage health information efficiently
- Distinguish sense from non-sense
- Provide evidence based health care
- Summarize and integrate results from individual studies
- Determine if new studies are needed
Systematic Review: Role
- Identifies original research
- Facilitates critical appraisal of original research
- Summarizes large body of knowledge
- Estimates treatment/exposure effects
- Promotes evidence-based medicine
- Identifies research gaps
Systematic Review: Steps
- Objectives and Protocol
- Literature Search
- Quality Assessment
- Assemble Data Set
- Data Synthesis
- Perform sensitivity analysis, subgroup analysis, publication bias analysis, if appropriate
- Conclusions
Systematic Review: Steps - Objectives and Protocol
- Objectives/study question (PICO/PECO)
- Inclusion/exclusion criteria for individual studies
- Literature search and data analysis plan
- Can register on PROSPERO website
- No REB required
Systematic Review: Steps - Literature Search
- Database, search strategies, screening/reading studies
- Identification of all relevant studies
- Structured search strategy
- Title/abstract screening
Systematic Review: Steps - Quality Assessment
- Tabulate study characteristics and assess quality
- Study Characteristics (design, participants, interventions, outcomes)
- Study Quality Assessment (RCT, use Cochrane Risk of Bias)
- Judging Methodological Quality (focus on internal validity)
Systematic Review: Steps - Assemble Data Set
-Extraction of data and data entry
-Full text review
-Data Extraction
+Discrepancies resolved by discussion/external referee
+Write to researchers to get additional info
+Estimate data
Systematic Review: Steps - Data Synthesis
-Statistics and heterogeneity
-Qualitative Data Synthesis: Summary information based on words, NOT stats (i.e.. participants, interventions, outcomes, study design)
-Quantitative Data Synthesis: Statistical analysis combining the results of independent clinical trials considered by the analyst to be combinable
+Statistical model can be Fixed or Random Effects
Systematic Review: Interpreting Treatment Effects - Statistical Measures of Effects for Dichotomous Outcomes
-Relative Risk: Relevant event rate
RR = [a/(a+b)]/[c/(c+d)]
-Risk Difference: Absolute difference in event rate
RD = a/(a+b) - c/(c+d)
-Odds Ratio: Relative number of individuals that fulfill the criteria for a given outcome divided by the number who do not
OR = (a/b)/(c/d)
+Approximates RR when baseline probabilities of the outcome are low (less than 0.1-0.2)
-NNT = 1/RD
Systematic Review: Interpreting Treatment Effects - Statistical Measures of Effects for Continuous Outcomes
-Mean Difference: Weighted difference in mean between intervention and control groups
MD = Mean (int) - Mean (cont)
-Standardized Mean Difference: Absolute difference in mean value between intervention and control divided by SD
Systematic Review: Interpreting Treatment Effects - Testing for Heterogeneity
- Inspect scatter in data points and overlap in CI
- Forest Plot - Check results of I2 and chi-squared tests
- I2 estimates percentage of variability in results across studies that is likely due to true differences in treatment effects (not chance)
- Chi-square estimates the variation between results of trials due to chance