Introduction to Systematic Review and Meta-Analysis

Session Aims

  • Introduce systematic review and meta-analysis
  • Define what systematic reviews and meta-analyses are
  • Explain the necessity of systematic reviews and meta-analyses in research
  • Elaborate on the processes involved in conducting these reviews
  • Enhance ability to utilize and evaluate existing systematic reviews and meta-analyses
  • Note: Participants will not be expected to conduct their own reviews

Outline of the Session

  • Key aspects of systematic reviews
  • Interactive quiz using Menti
  • Combining results in a meta-analysis
  • Interpreting forest plots through practical exercises
  • Discuss impacts of systematic reviews and meta-analyses

Importance of Reviewing Health Research

  • Biomedical journals publish hundreds of thousands of articles annually
  • Researchers face challenges keeping up with the volume of articles
  • There is a clear need for effective summaries that synthesize research findings

What is a Systematic Review?

  • Definition: A systematic review compiles all evidence addressing a specific research question
  • Employs explicit, systematic methods to reduce bias
  • Aims to provide more reliable findings for conclusion drawing and decision-making
  • Source: Cochrane Handbook for Systematic Reviews of Interventions

Need for Systematic Reviews

  • Mostly assess treatment effects on diseases or conditions
  • Guide clinical practice and inform new research
  • Facilitate informed patient choices and influence health policy
  • Preference for evidence from randomized controlled trials (RCTs)

Types of Systematic Reviews

  • Systematic reviews address various questions:
  • E.g., MRI diagnostics in acute appendicitis in children
  • Potential evidence types: cohort studies, case-control studies, patient series, prognostic models, diagnostic test accuracy studies

Focus of Today's Discussion

  • Emphasis on systematic reviews and meta-analyses related to treatment effects
  • Evidence primarily from RCTs
  • Use of summary (aggregate) data from various reports and papers
  • Methodological principles are consistent across different systematic review inquiries

Key Aspects of Systematic Reviews

  1. Clear Objectives and Eligibility Criteria
  2. Search Strategy: Identify all relevant studies
  3. Consistent Data Collection: Uniform data gathering across studies
  4. Assessment of Validity and Bias: Evaluate the quality of studies and potential biases
  5. Synthesis of Study Characteristics and Results: Engage in meta-analysis
  6. Structured Presentation of Results: Follow systematic guidelines for clear reporting

Using PICOS Framework

  • Population: Target population of study
  • Intervention: Treatment being evaluated
  • Comparison: Control group or alternate treatment
  • Outcomes: Measurable effects or results
  • Study Design: Types of studies included in the review
  • Example: Studying communication strategies in young patients with Down syndrome

Defining a Clear Question

  • A well-defined question should succinctly state:
  • Aim: “To assess the effects of [intervention] for [disease] in [population] on [specific outcomes]”
  • Includes precise study eligibility criteria to delineate participants, interventions, and outcomes

Ensuring Similarity Among Studies

  • Eligibility criteria mitigate differences (heterogeneity) between trials
  • Aim to include trials that address similar questions to yield meaningful results, even if slight variances in factors exist (e.g., age, geography, dose)

Developing Search Strategies

  • Systematic reviews necessitate thorough searches across multiple databases to locate eligible studies
  • Rely on:
  • Broad scope databases (e.g. Medline, PubMed)
  • Specialized resources (e.g. CINAHL, Psych Info)

Screening the Studies for Eligibility

  • Screening involves:
  • Removing duplicates and irrelevant studies based on predefined criteria
  • Example: In prostate cancer assessment, screening reduced 5143 records to 35 eligible trials

Managing Search Results

  • Crucial for tracking and recording studies
  • Utilize reference management software (e.g. Endnote)
  • Systematically organize eligible and ineligible articles

Consistent Data Collection Requirements

  • Collate relevant data defined by the systematic review’s aim
  • Rely on data from various potential sources (e.g. conference abstracts, trial protocols)
  • Use predefined forms (paper or electronic) for uniformity in data extraction

Challenges in Data Obtaining

  • Possible obstacles:
  • Old studies, language barriers, incomplete reporting of outcomes
  • Strategies: Reach out to trialists for supporting data and results

Understanding Bias in Clinical Trials

  • Bias = Systematic error or deviation from true results
  • Potential impact on study results:
  • May lead to overestimations or underestimations of treatment effect
  • Varies in effect significance

Types of Bias to Consider

  • Publication Bias: Favorability toward publishing trials with significant findings
  • Design and Conduct Bias: Bidirectional influence based on trial execution quality

Assessing Bias Impact in Reviews

  • Importance of evaluating the impact of bias on the individual trials and overall review outcomes using tools like Cochrane Risk of Bias 2 tool

Steps for Conducting a Systematic Review

  1. Define questions and criteria with PICOS
  2. Identify and retrieve relevant studies
  3. Extract data consistently from eligible studies
  4. Assessors of quality/risk of bias

Meta-Analysis Overview

  • Definition: Quantitative method of combining results from related trials
  • Provides an average treatment effect
  • Enhances the power to detect differences in treatment effects
  • Offers reliable estimates and reduced confidence intervals

Forest Plots in Meta-Analysis

  • Visual representation to compare trial outcomes:
  • Uses hazard ratios to contrast treatment with control outcomes over time
  • Important for understanding overall treatment effects in clinical research

Evaluating Consistency and Strength of Evidence

  • Assess direction and significance of effects across studies
  • Consider the size of the effect, confidence intervals, and number of studies involved

Randomized Controlled Trials Specifics

  • Used to evaluate treatment effects against standards or placebos
  • Address various endpoints including continuous measures and binary outcomes

Conclusion: Systematic Review Impacts

  • Systematic reviews play crucial roles in shaping clinical practices and policies, driving new research initiatives, and quickly updating treatment guidelines based on new evidence.
  • They are foundational in gathering, evaluating, and synthesizing clinical evidence.