Evidence Based Dentistry Flashcards
What is a Systematic Review?
A type of literature review that uses systematic methods to collect secondary data, critically appraise research studies and synthesise studies
What are the benefits of systematic reviews?
Saves readers time
Provide reliable evidence
Resolve inconsistencies
Identify gaps
Identify when questions have been fully answered
Explore differences between studies
What are the key characteristics (5) of a systematic review?
Well formulated question
Comprehensive data search
Unbiased selection and abstraction process
Assessment of papers
Synthesis of data
Why are systematic reviews important?
Reduce large quantities of information into manageable portions
Formulate policy and develop guidelines
Efficient use of resources
Increased power/precision
Limit bias and improve accuracy
What is the Cochrane Collaboration?
Global independent network
Provides a powerful tool to enhance your healthcare knowledge and decision making
Gathers and summarises the best evidence from research to help you make informed choices about treatment
In forest plots what does I squared value represent?
What % is acceptable
Level of statistical heterogeneity
<50% is acceptable
What does PICO stand for?
Participants
Interventions (exposure)
Comparisons
Outcomes
What is more likely to happen to statistically significant ‘positive’ results?
More likely to be published (publication bias)
More likely to be published rapidly (time lag bias)
More likely to be published in English (language bias)
More likely to be cited by others (citation bias)
What does unbiased selection and abstraction process include?
Selection of relevant papers
Data extraction to a predefined data extraction form
Process should be conducted independently by at least 2 reviewers
Clear description of reasons for exclusion
Adequate description of included studies
Details of studies funding sources
What are composite scales?
‘Quality’ Assessment Tool
Assign numerical value to individual items to provide overall estimates of quality
NOT preferred method
What is a component approach?
‘Quality’ Assessment Tool
Assess relevant methodological aspects individually (e.g. randomisation, blinding, drop-outs)
PREFERRED method
What is bias?
Bias determines the extent to which results of studies can be believed (low risk of bias= higher belief in results)
What is included in a risk of bias assessment for RCT’s?
Sequence generation (selection bias)
Allocation concealment (selection bias)
Blinding (participants/outcome assessors)
Incomplete outcome data (attrition bias)
Selective outcome reporting (reporting bias)
Other bias
What type of information does a meta-analysis include?
Quantitative
What is a meta-analysis?
The process of using statistical methods to combine the results of different studies
Aim is to integrate the findings, pool the data, and identify the overall trend of results
Calculates a treatment effect based on pooled data from a group of studies
What are the potential advantages of a meta-analysis?
Increase in power
Improvement in precision
Ability to answer questions not posed by individual studies
What is Dichotomous data ?
Binary data
Illness or not/death or not/birth or not
Comes in one of 2 forms (either are or are not)
What is Continuous data?
Blood pressure/weight/amount of pain
Quantitative data that is measured to the precision of what you are measuring
What sorts of summary statistics are included in Dichotomous data?
Odds ratio
Risk ratio
Percent risk reduction or relative risk reduction (RRR)
Risk difference, or absolute risk reduction (RD)
Number needed to treat (NNT) (1/RD)
What kinds of summary statistics come under Continuous data?
Weighted mean difference
Standardised mean difference
When weighting studies what is more weight given to?
More participants
More events
Lower variance
What is the line of no effect in forest plots?
Vertical line in the middle where the intervention and control have the same effect
If the study sits here there is no difference between the treatment and the control
What shape is given to the pooled analysis in a forest plot?
Diamond
What is Heterogeneity?
Refers to the variability or differences observed among studies
What is clinical heterogeneity?
Variation in participants, interventions, outcomes and study design
Ways the different studies are conducted
What is methodological heterogeneity?
Variation in methods used in studies e.g. quality of allocation concealment
What is statistical heterogeneity?
How does this appear in forest plots as?
Excessive variation in the results of studies
Variation in treatment effects above that expected by chance
May appear in a forest plot as poor overlap of confidence intervals
What is the test for heterogeneity?
What P value demonstrates statistically significant heterogeneity?
Chi-squared test of heterogeneity
P<0.1 demonstrates statistically significant heterogeneity
What does GRADE stand for? What is it used for
Grading of Recommendations Assessment, Development and Evaluation
Evaluates the quality of the body of evidence
What does a summary of findings table include?
Summary of the key findings from a systematic review
It presents quality of the evidence, magnitude of the effect and reasons behind the judgements
What is incidence?
Number of new cases over a specific time
What is prevalence?
Number of cases at a time
