EBM Flashcards
Hierarchy of study design
Systematic reviews & meta-analyses Randomised Controlled Trials Cohort studies Case-control studies Ecological studies Descriptive/cross-sectional studies Case report/series
Evidence Based Medicine
conscientious, explicit and judicious use of current best evidence in making decisions about the care of individual patients.
Role of EBM in clinical medicine
Clinical findings Aetiology Clinical manifestations of disease Differential diagnosis Diagnostic tests Prognosis Therapy Prevention
Criticism of EBM
Time consuming
Jargon is used inappropriately
Why EBM matters to clinicians
Better service for patients Patient care + safety Medical knowledge Revalidation Professionalism
Systemic reviews + meta analysis
Aims to answer defined research question by collecting & summarising empirical evidence that fits pre-specified eligibility criteria.
Advantages to systemic approach
Transparent inclusion of studies
MA increases power of study
May identify lack of adequate evidence
Randomised Control Trial
Selection for people you want to experiment on.
GOLD STANDARD for clinical trials & surgical interventions.
RCT disadvantages
–With some treatment, effect might be weak so trials may need to be very large to demonstrate an effect.
–Expensive!
Cohort
Individuals selected on basis of exposure status &
followed over time to allow frequency of occurrence of outcome of interest in exposed & non-exposed groups to be compared.
Time period of cohort
Prospective
What can be calculated from cohort studies
Relative risk
Incidence
Which came 1st incidence or risk factor
Advantages of cohort studies
looks at multiple outcomes
follows natural history of disease
minimise bias in estimating exposure as prospective
Disadvantages of cohort studies
Inefficient for rare diseases
Expensive
Time consuming
Loss of follow-up =Bias
Case control studies
Selection based on whether or not they have outcome of interest
Exposure (risk factor) status explored to establish whether exposure is more common in the case or control group
Case control studies determine
whether an exposure is associated with an outcome
What can be calculated from a case control study
Odds ratio
Advantages of case control study
Quick
Cheap
Good for outbreaks of infectious/ rare disease
Can investigate many exposures simultaneously
Disadvantages of case control study
Problems of selection of controls Subject to recall bias Uncertainty of exposure-disease time relationship Poor for rare exposures Can't calculate incidence directly
Case control study time period
Retrospective
Ecological studies
Type of descriptive study
Uses correlations between different populations, using different exposures
Descriptive/ cross-sectional studies
Based on routinely collected data. Difficult to show causal relationship
Descriptive/ cross-sectional study example
Survey
Census
Case report/ series
–Description of single case/ series of cases.
–NOT evidence used to support practice BUT sometimes useful in picking out new syndromes or conditions.
