Thinking critically about clinical evidence Flashcards
What is a systematic review
- Structured method of reviewing research on a specific research question
- Provides evidence for treatment
- May include statistical synthesis called meta analysis
What are questions asked by Systematic reviews
Effectiveness:
- Does intervention work or not?
- Why does it work or not?
Comparing Interventions:
- How does intervention work?
What are the main features of a systematic review
Transparent: due to explicit search strategy and criterion based selection
Comprehensive: search more than one database, range of search terms and often including unpublished literature
- Formal cortical appraisal process
- Less subjective to bias than a traditional narrative review
- Protocol driven
What are the advantages of a systematic review
- Replicability
- Reducing bias
- Comprehensive + addresses publication bias
- Studies with both positive and negative findings included
- Identifying gaps in current research
- Providing reliable biases for decision making
What is The Cochrane Collaboration
- International non profit organisation that prepares, maintains, and disseminates systematic up to date reviews of healthcare interventions.
- Cochrane library; publishes systematic review, guidance on how to carry them out, software for analysis, restricted to medical/ health topics, mainly about assessing findings from trials
Meta analysis Effect Size
- Unaffected by sample size
What is Meta analysis
- Results from individual studies pooled to a calculate the average effect size
- Summarises the effectiveness of an experimental intervention
- A systematic review does not have to include a meta analysis
Limitations of systematic review & meta analysis
- Publication bias means many non significant study’s may be excluded
- Language bias if limited to English
- Loss of granularity
- Findings can’t necessarily be applied to individual cases (e.g. clinical settings)
What are Randomised Control Trials
- Gold standard clinical trials
- Patients Randomly assigned to treatment or placebo, equal chance of being either
- double blind
- Control group isn’t ethical
- Larger effect size
- Standard treatment comparison
What is a case control study
- Study which compares two groups of people, those with the disease or condition under study and a very similar group of people who do not have the disease or condition
- Advantages: cost effective, they can be used to study outcomes or diseases that are rare
- Disadvantages: potential risk factors are collected retrospectively and as a result may give rise to bias, selecting suitable control group
Cases- exposed or unexposed
Control - exposed or unexposed
Cross sectional Study
- Data collected on the whole study population at a single point in time to examine the relationship between disease and other variables
- Sample size has to be large to estimate prevalence of conditions with adequate precision
