Block 4 Week 3: Systematic Reviews Flashcards
Define a systematic review
A review of a clearly forumulated question that uses systematic & explicit method to identify, select and critically appraise relavent research & to collect and analyse data from the studies that are included in the rewview
Why have systematic reviews/ why are they important ?
- Identify which forms of healthcare work and do not work, and which are harmful
- Clinicians /Busy HCP need quick effective ways of identifying what works best for pt
- Systematic reviews help drirect healthcare policies and are the bedrock of clinical guidelines e.g. NICE
- Health care providers need to be evidence based to ensure practice is up to date
Important:
- synthesises results from similar randomised trials but in a reliable way (so is systematic). It includes steps to minimise bias in all parts of the process.
- Systematic reviews are the best way of staying ahead in a field of interest
A systematic review is…
- A summary of all the available evidence of a particular topic
- Based on a clearly defined search of the literature and uses explicit criteria to appraise the quality
- Stringest study inclusion and exclusion criteria
- The findings are analysed using validate methods
What are the three key functions of a systematic review?
Synthesise the evidence
Understand hetrogeneity in treatment effects
Set the research & practice agenda
In the hierachy of evidence where do systematic reviews sit?
- Systematic reviews sit at the top of the hierarchy of evidence
- Followed by randomised control trials
- Cohort studies
- case control studies
- then case reports/ case series
- editorials and expert opinion
What steps need to be taken before conducting a systematic review?
- Define the purpose the of the review
- define the nature of the research question
- Define population included
- Team factors –> need 2/3 colleagues to duplicate review independently
- Need a clear research strategy
- what studies will you include?
- what are the outcomes that you are interested in?
- what methods of analysis will be used? e.g. metanalysis or narrative
- what are the expected conclusions and what is its added value (to research or clinical practice?)
What are the steps to a systematic review?
- Rationale/ Familiarise with process
- Question
- Protocol
- Literature search
- Screening
- Eligibility
- Data abstraction
- Quality assessment
- Analysis
- Summary& Writeup
Systematic review: Rationale/ Familarise with protocol
Rationale: Thinking of the research qu in context of what is already known:
- What is already known so far
- Similar reviews happening/ been done?
- Awareness of possible nature and volume of outcome
Familarise with Protocol:
- Start preparing protocol
- Follow reporting guidelines eg: PRISMA-P
SR step 2: Question
Step 2 of systematic review is defining the research question and translating it into the review. Uses framework.
For quantitative reviews uses: PICOS (study design= S)
Population
Intervention
Comparator
Outcome
Study design
For qualitative uses SPICE:
(Setting, Population, Intervention, Comparison, Evaluation)
SR step 3: Protocol
Informed by & refined from research question
Include:
- Search strategy
- Inclusion/ Exclusion criteria
- Data extraction
- Risk of bias assessment
- Analysis/ Synthesis plan
- Presentation and Interpretation
SR step 4: Literature Search/ Study Retrieval
- Identify where you plan to search –> appropriateness of databases
- Identify search terms
- Search techniques
- Number of records identified through database search/ other sources
SR: Screening
- Compile all the results of the papers found in the databases used for your literature search
- Remove any duplicates, identify sudies relevant to research question (better to be overinclusive at this point.)
- Record number screened (Include (if seems relevant)/ Exclude) and all references
- Assessed by x2 reviewers
SR: Eligibility
- Obtain full texts of the studies that were thought to be relevant
- Then asses against each domain informed by research framework: PICO/SPICE.
Yes to all domains, included. No to one domain–> Excluded. Unsure speak to colleague/ 3rdreviewer
- Inclusion/Exclusion Number recorded
- Excluded record with reason
SR: Data Abstraction
Extract data relavant to question
SR: Quality Assessment
•Suitable tool: Inform analysis & Interpretation
Look for Bias (& summarise for each study)
- Selection –> any bias in the way participants are selected?
- Performance –> any systematic differences in care provided to participants in comparison vs intervention?
- Detection –> were the researchers blinded to the allocation?
- Attrition –> drop out, any differences in intervention vs control drop outs?
- Reporting –> selective reporting of study outcomes?
- Other –> e.g. funding (drug intervention funded by pharmaceutical company, declare conflict of interest?).
Discuss the types of Quality Assessment types of Bias
Selection Bias:
- Systematic bias in the way participants are selected
Performance Bias
- Systematic differences in the care provided to the participants in the comparison groups other than the intervention under investigation
Detection Bias
- Systematic differences between the comparison groups in outcome assessment
Attrition Bias
- Systematic differences between the comparison groups in the loss of participants from the study
Reporting Bias
- Selective reporting of study outcomes
Other Bias
- Funding, error is results
SR: Analysis
Define Meta-Analysis
Quantitative:
- Meta-Analysis if possible
- Results of individual studies combined to produce overall statistic.
- Subject to any biases during selection process –> Mathematically precise but clinically misleading result
- ForestPlot
Qualitative:
- Narrative Analysis
Meta-Analysis
What are looking for?
What is hetrogeneity, how is it measured? Why is it important?
Metanalysis:
- Outcome being examined
- Time frame for the outcome? (how long study follows participants for)
- Summary effect size being used? (i.e mean difference or risk ratio).
- Number of trials included?
- Heterogeneity in the comparison? i.e differences in the ethnicites of the populations used or the setting of the study (clinical vs in the home).
- Heterogeneity:
- I2 understand heterogeneity
- Percentage of variation between studies in meta-analysis due to differences between studies & not just sampling error
- 0%, 25% low, 50% moderate, 75% high
- Important:shapesunderstanding pooled effect- Is this true effect or the average effect in a distribution
SR: Summary & Write up
Presentation & Interpretation of findings
What are the types of Bias that may occur in a systematic review?
- Duplicate bias (trial with 5 publications referring to same trial, count as 1 trial)
- Language bias –> restrict review to english only, miss other languages
- Outcome Reporting bias –> go back to protocol and find out outcomes diverted from what you intially planned
- Citation bias –> researchers so other researches favours, picked up studies that are cited a lot
- Publication bias
- Funnel plot for 10 or more studies
- Should see equal distribution
- Bias: Trial with significant result produced –> Asymmetrical funnel plot
What does a high quality SR consist of?
- Search Strategy: Inclusive & Reproducible
- Flow of all studies/papers-PRISMA
- How inclusion & Exclusion criteria applied (PICOS/ SPICE)
- Table of characteristics of studies (Included & Excluded- Reasons)
- Quality assessment: Cohesive synthesis/ Analysis (+/- meta-analysis)
- Practical application of findings
- Strengths & Limitation of SR
