Midterm Flashcards
The conscientious, explicit, and judicious use of current based evidence in making decisions about the care of individual patients
EBM
integrating individual clinical expertise with the best available external clinical evidence from systematic research
EBM practice
EBM is the integration of what?
best research evidence, clinical expertise, and patient values (concerns)
what are the 5 steps to applying the medical literature to patient care? (evidence cycle of EBM)
- ask
- acquire
- appraise
- apply
- act
what are the 2 different types of study design?
- observational
2. analytical or experimental
what does an observational study design entail?
does not involve any intervention or experiment; seeks to measure the frequency in which disease occur or collect descriptive data on possible casual factors
what are 5 types of observational study designs?
Ecologic, cross-sectional, case report/case series, case control, cohort
what does an analytical or experimental study design entail?
manipulation of the study factor (exposure) and randomization of subjects to treat or control groups; attempts to specify in more details the causes of a particular disease or the effect of an intervention
what are 2 types of analytical/experimental study desgins?
Non-randomized control tried, RCT (double blind, placebo controlled)
describe the hierarchy of evidence
Bottom to top: Studies (original journal articles) Syntheses (systematic reviews) Synopses (evidence based jouranl abstracts) Summaries (evidence based textbooks) Systems (computerized decision support)
describe the hierarch of study design
Bottom to top: Editorials/expert opinions Case series/Case reports Case control Studies Cohort studies RCTs Systematic reviews
What Study type?
Mathematically pools data from individual studies (does not have be as ‘all-inclusive’)
Meta analysis
What Study type?
Starts with patients with an exposure (self-selected) and follows them forward to an outcome
*Prospective
Cohort
What Study type?
Experimental design that introduces an intervention to modify the course of a disease
RCT
What Study type?
Starts with an outcome or disease and looks backwards to identify a possible exposure
*retrospective
Case control
What Study type?
Call attention to an unusual association, adverse event, or a unique case
Case series/case report
What Study type?
Focuses on a clinical topic, conducts a thorough review of the literature, validates quality of the studies and summarizes the data
Systemic Review
ie. Cochrane Database
What are strengths of a Meta Analysis and Systematic Review?
- summarizes literature
- prospective
- validates smaller studies
What are weaknesses of a Meta Analysis and Systematic Review?
- time consuming
- difficult to combine studies
- publication bias (positive studies are more likely to be published)
- requires studies to be ‘similar enough’
What are strengths of a RCT?
- randomization
- controls for bias
- control over exposure
- best for proving efficacy
What are the weaknesses of a RCT?
- expensive
- ethical considerations
- time consuming
What are strengths of a Cohort?
- observing patients
- prospective
What are the weaknesses of a Cohort?
- time consuming
- possible cofounders
- can NOT prove causation
- Recall bias
What are strengths of a Case control?
- quick
- cheap
- convenient
- Good for rare disorders
- ethical
What are the weaknesses of a Case control?
- Based on recall
- Confounders
- Difficult to choose control groups
What are strengths of a Case series/ case report
- Identify new disease
- preliminary study
What are the weaknesses of a case series/ case report
- no control group
- no comparison
ID the highest quality of study to answer a clinical question from highest to lowest (the prevention and treatment hierarchy) (7)
- N of 1 randomized trial
- systematic reviews of RCTs
- Single RCT
- Systematic reviews of observational studies
- single observational study
- physiological studies
- Unsystematic clinical observation
What study types are best to answer a clinical question about:
Therapy
Systematic review/Meta analysis > RCT > Prospective Cohort
What study types are best to answer a clinical question about:
Diagnosis
Prospective, blind comparison to a gold standard
What study types are best to answer a clinical question about:
Prognosis
Cohort study > Case control > case series
What study types are best to answer a clinical question about:
Etiology/harm
RCT > Cohort> case control > case series
What study types are best to answer a clinical question about:
Prevention
RCT > cohort > case control > case series
What study types are best to answer a clinical question about:
Cost
Economic Analysis
What study types are best to answer a clinical question about:
Clinical Exam
Prospective, blind comparison to a gold standard
Define the parts of a PICOTT question
P- patient/population/problem
I- intervention (prognostic factor, exposure)
C- comparison
O- outcome (you would like to measure or achieve)
T- type of question
T- type of study wanted
what is a likelihood ratio?
the probability that a test result will occur in a patient WITH DISEASE compared to the probability that the same result would occur in a patient WITHOUT DISEASE
usually for diagnostic tests to let you know how ‘good’ your diagnostic test is
likelihood ratio
Draw out the 4 square table for diagnostic tests
across top: disease +, disease -
1st column: test +, test -
a-b = (TP - FP)
c-d = (FN - TN)
true positive rate
and calculation
sensitivity
a/(a+c)
how to calculate false negative rate
1- sensitivity
true negative rate
and calculation
specificity
d/(b+d)
how to calculate a false positive rate
1- specificity
TPR/FPR
LR +
FNR/TNR
LR -
LR
rule out
LR > 10 means
rule in
how much more likely?
LR 2 –> 5 –> 10
Increase probability by
15% –> 30% –> 45%
how much more likely?
LR 1/2 –> 1/5 –> 1/10
decrease probability by
15% –> 30% –> 45%
what is a relative risk
the ratio of risk in the treated group (Y) to the risk in the control group (x)
RR = Y/X or (X-Y)/X x 100%
how do you calculate the RRR
1- RR = RRR
The percentage reduction in risk in the treated group (Y) compared to controls (X)
Relative Risk reduction (RRR)
chance of benefit
Absolute Risk reduction
the difference in risk between control group (X) and the treated group (Y)
Absolute risk reduction
how do you calculate ARR?
ARR = X- Y
How do you calculate NNT`
NNT = (100/ARR) x 100%
a NNT of 15 means what?
you must treat 15 patients to prevent 1 adverse outcome
how accurately a test identifies those WITH disease
Sensitivity
“Rules in”
How accurately a test identifies those WITHOUT disease
specificity
“rule out”
How do you calculate sensitivity and specificity
Sensitivity = TP / (TP + FN) Specificity = TN / (TN + FP)
the probability that the patient has the disease when the test result is positive
PPV
the probability that the patient does NOT have the disease when the test result is negative
NPV
How do you calculate PPV and NPV
PPV = TP / (TP + FP) NPV = TN / (TN + FN)
How does prevalence of a disease affect sensitivity?
no impact
How does prevalence of a disease affect specificity?
no impact
How does prevalence of a disease affect PPV?
increases as prevalence increases
How does prevalence of a disease affect NPV?
decreases as prevalence increases
What tells you how precise the results are?
confidence interval
a narrow ranged CI means what?
the more accurate the researcher believes the point estimate to be
a wider ranged CI means what?
the less sure the researcher is of the actual value
When is a CI statically significant?
when P
When is a CI suggestive of a beneficial trend?
RR
When is a CI suggestive of a harmful trend
RR > 1
When is a CI inconclusive?
P > 0.5 AND crosses 1
