Hosam Mohamed-
Evidence-Based Medicine
1.Convert our information needsinto answerable questions2. Track down the best evidenceto answer these questions3. Appraise the evidencecritically to assess its validityand usefulness4. Implement the results of thisappraisal in clinical practice5. Evaluate our performance
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decision-making by: anecdote, press cutting, gobstat, cost-minimization
What are some barriers to EBM?
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Decision-making by anecdote
-storytelling, personal-experiences, and past successes
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Decision-making by press cutting
-chasing new articles and editorials to replace standard practice
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Decision-making by GOBSAT
-consensus statements and expert opinions (key-opinion leaders)
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Decision-making by cost-minimization
-cheapest option no matter how effective it is.
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b; prospective design
Which of the following is NOT an advantage of RCT? Correct the wrong statement.
a) rigorous evaluation of a single variable
b) retrospective design
c) use of hypotheticodeductive reasoning
d) minimizes bias
e) allows for meta-analysis
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expensive, time consuming, bias
What are the biggest disadvantages associated with RCT?
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selection bias
-selection of participants unrepresentative by the condition.
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Uptake bias
-Limited interest in the study, or ability to participate in it, regarding key groups
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Performance Bias
Differences in what is provided to the groups over and above the intervention being tested
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Detection bias
Differences between groups in how outcomes were assessed
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Attrition Bias
When one group has many more withdrawals or “drop-outs” than the other
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Publication bias
Selective publication of positive results
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Cohort study
-Two or more groups of people are selected on the basis of differencesin “exposure” and follows to see how many develop a particular“outcome”.
-usually a time component
-retrospective & prospective
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Inception cohort
• Prognosis study to follow early stage diagnosis to particular outcomes• Helps us determine incidence, time course of outcomes or disease
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case control
-patients with a particular disease or condition are identified and matched with controls
-data is collected retrospectively; on exposure to causal agent of disease
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studying rare diseases or genetic associations
What are case-control studies great for?
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only establishes association; not causation
What is a potential limit associated with case-control studies?
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defining cases & bias
What are difficulties in case-control studies?
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case reports
-A case report describes the medical history of a single patient in theform of a story
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cross-sectional surveys
Representative sample ofparticipants is recruited andthen interviewed, examined, orotherwise studied to gainanswers to specific questions• Data is collected as a singlepoint in time, may be framedprospectively or retrospectively
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systematic review/meta, rct, cohort, case controlled, case series, background/expert
Order the quality of evidence from highest to least?
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bias
is defined by epidemiologists as anything that systematicallyinfluences the conclusions about groups and distorts comparisons
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selection, performance, attrition, detection
What are sources of Bias in RCTs?
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selection of comparable control group
What are sources of bias in Observational studies?
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intent to treat
All randomized participants are analyzed in the group to which they were originallyassigned, regardless of whether or not they completed the study or adhered to theassigned treatment• ITT analysis aims to preserve the integrity of the randomization process and reduce bias.
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per protocol
includes only participants who completed the study as intended and followed theassigned treatment protocol.• PP analysis may lead to bias if only a certain subgroup of participants who adhered well to thetreatment protocol are analyzed
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e
Which studies are best at establishing efficacy of interventions; more concerned with the actual therapy the patients will be receiving?
a) cross-sectional design
b) Longitudinal design
c) cohort
d) case control
e) rct
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a
Which studies are preferred to determine if a diagnostic test is valid and reliable?
a) cross-sectional design
b) Longitudinal design
c) cohort
d) case control
e) rct
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a
Which studies are preferred to demonstrate if tests can be applied to large populations or detect disease at a pre-symptomatic stage?
a) cross-sectional design
b) Longitudinal design
c) cohort
d) case control
e) rct
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b
Which studies are preferred to determine what is likely to happen to someone whose disease is picked up at an early stage?
a) cross-sectional design
b) Longitudinal design
c) cohort
d) case control
e) rct
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c, d
Which studies are preferred to determine whether an exposure leads to the presence of disease?
a) cross-sectional design
b) Longitudinal design
c) cohort
d) case control
e) rct
