Assessing Evidence in Medicine Flashcards
What are the functions of critical appraisals?
Interpret conflicting conclusions to obtain consensus
Inform guidelines
Translate research into real life clinical medicine
What are the types of study design?
Experimental = systematic review, randomised controlled trials
Observational analytical = cohort, case-control, cross sectional stud
Observational descriptive = case report, case series
What is key to critical appraisal?
Assessing methodology
What is the CONSORT statement?
Minimum set of recommendations for reporting randomised trials = evidence based
What is the principle of intention to treat?
Principle that the patient is analysed in the group they were randomised in irrespective of subsequent changes
What are some features of intention to treat?
Preserves removal of bias created by randomisation to give fair comparison
Essential for integrity of trial and tends to reflect real world
What are some features of per-protocol?
Patient is analysed in treatment group they actually received = more concerned with mechanism and science than clinical practice, may not reflect real clinical world
How are results presented?
Results assessed using statistical inference testing
Test used depends on type of data
Results declared as a difference between groups with a 95% confidence interval
What is the relationship between p-value and the strength of evidence against the null hypothesis?
p>0.1 = weak p<0.05 = accepted significant p<0.01 = very strong
How is the absolute risk calculated?
Number of events in treated/control groups divided by the number of people in that group
What is the main problem with observational data?
Confounding is a big issue because data isn’t randomised
How is relative risk interpreted?
RR >1 = exposure harmful
RR <1 = exposure protective
RR of 1 = exposure similar to unexposed
RR of 1.7 = 70% increase
What are the different types of cohort study?
Prospective = cohort followed forward in time from present Retrospective = cohort formed in past and followed up to present
What are the advantages of a cohort study?
Temporality, no recall bias, can study multiple outcomes, can measure incidence
What are the disadvantages of a cohort study?
Requires large investment of resources, needs large sample sizes, loss of follow-up bias, inefficient for rare diseases, uncontrolled confounding
