Week 3 Flashcards
Key steps using population based research to help with clinical decisions
Assess: formulate a clear clinical question (PICO), identify the study design that would provide the most accurate answer
Access: search for and retrieve the research
Appraise: identify strengths and weaknesses of the research you find and understand what the results mean
Act: apply the evidence, taking into account its limitations, alongside other information eg patient preference
Systematic reviews
Review all of literature
On one particular topic/question
Using scientific methods
Reasons for differences between RCTs
Chance
Differences in people
Differences in intervention/comparator
Differences in care other than that being investigated
Differences in the way treatment effects are assessed
Differences in follow up
Reporting of the available evidence
Selection from the available evidence
Publication bias
When the publication of research results depends on their nature and direction
-positive results bias- when authors are more likely to submit or editors accept, positive than negative or inconclusive results
-outcome reporting bias- when several outcomes within a trial are measured but are reported selectively depending on the strength and direction of those results
Issues
Large volume information
Low quality info drowns out high quality info
Cannot find/read the right evidence for my/my patients/ my organisations specific needs
Must critically evaluate the methodological rigor and statistical analyses of a study
But:
Limited time to master required skills
If have skills no time to read all papers
Benefits of reviews
Volume of literature condensed
New info made accessible
Some reviews are extremely good and have taken considerable time to find all the relevant info and review the topic well
Systematic review
The research method generally used to synthesis multiple pieces of research evidence on the effectiveness of a treatment
Review of all literature
On one particular topic
Using scientific methods
Clear question being addressed by the review
An explicit and detailed statement of the methods used
Comprehensive ascertainment of the literature relevant to the review question
Steps to reduce bias in the review process/ documenting of any bias
With or without:
An appropriate numerical summary of the size of effect with confidence intervals
Stages in a systematic review
Define question
Write protocol
Search for evidence/studies
Select relevant studies from search
Appraise studies
Extract, analyse and summarise data
Interpret review results
Discussion and conclusions
Forest plot
The size of the square relates to the weight given to the study in the meta-analysis
Middle of square represents the results
Line represents the 95% confidence interval
Line of no difference between trial groups
The diamond is the summarised result (meta analysis)
Systematic review v meta analysis
Systematic review: explicit methods to identify and review all of the literature on a specific topic in order to answer a specific question
Meta-analysis: statistical techniques used to combine the quantitative results from a number of studies
Advantages of systematic reviews
Can be the best source of evidence on the effects and effectiveness of healthcare interventions
Assimilation of large amounts of research evidence
Provide reliable unbiased estimates of effect
Increase precision of estimates of effects
Provide info about the generalisability and consistency of effect
Identify what info is missing
Useful for making decisions
Critical appraisal
The systematic identification of strengths and weaknesses of pieces of info
The application of that info within the limits identified
Internal validity:
- the degree to which the effect observed is attributable to the evidence, rather than any other cause (such as bias and other methodological problems of the review)
External validity:
-the degree to which the reviews conclusions apply to other persons in other places and at other times
Critical appraisal skills programme
3 part process:
-is the review trustworthy/ valid (internal validity)
Screening questions, detailed questions
-what were the reviews results
-how will the results help (external validity)
Relevance
Critical appraisal questions: SRs
Did the review ask a clearly focused question:
-consider if the question is ‘focused’ in terms of:
-the population studied
-the intervention given
-the comparator
-the outcomes considered
Did the review include the right type of study :
-address the reviews questions
- have an appropriate study design
Did the reviewer try to identify all relevant studies
How did the reviewers decide which studies to include and did they assess the quality (validity) of the included studies
If the results of the studies have been combined together was it reasonable to do so
How are the results presented and what is the main result
How precise are these results
Can results be applied to local population
Were all important outcomes considered
Should policy or practice change as a result of the evidence contained in this review
Heterogeneity
Methodological- different study designs combined
Clinical- different patients characteristics, settings interventions
Statistical- differences in reported effect size between the trials- look for statistical tests ( Chi 2, I2)
