Evidence Based Medicine Flashcards
EBM - formula
AR, ARR, RR, RRR, NNT, OR
Absolute risk
- number of events in treated or control group, divided by number of people in that group
Absolute risk reduction
- ARC - ART
Relative risk
- ART/ARC
Relative risk reduction
- (ARC-ART)/ARC
- 1 - RR
Number needed to treat
- 1/ARR
Odds ratio
- odds that a case was exposed/odds that a control was exposed
- AD/BC
Sensitivity
Sensitivity: how often a test shows pathology when it is present.
Specificity
Specificity: how often a test is normal when no pathology is present.
Negative predictive value
Negative predictive value: likelihood of the patient not having the disease when the test is negative.
Positive predictive value
Positive predictive value: likelihood of the patient having the disease when the test is positive.
Odds ratio
Odds ratio: association between an exposure and outcome.
● OR = 1 (no difference)
● OR >1 (negative)
● OR <1 (protective)
Number needed to treat
Number needed to treat: number of people needed to be treated to achieve one good outcome or prevent one adverse outcome.
False negative
False negative: diseased person incorrectly identified as healthy.
False positive
False positive: health person incorrectly identified as diseased.
Incidence
Incidence: number of new cases of disease occurring in a defined population within a specified period of time.
Prevalence
Prevalence: total number of individuals who have the disease at a particular time in a population.
Case control
Case control (retrospective): observational study in which two existing groups differing in outcome are identified and compared on the basis of some supposed causal attribute.
Cross-sectional
Cross-sectional (or prevalence): observational study that analyzes data from a population, or a representative subset,
at a specific point in time
Meta-analysis
Meta-analysis: systematic assessment of randomised controlled trials by merging data to draw a ‘firmer’ conclusion from larger numbers or subjects.
Cohort study
Cohort (or prospective): longitudinal study that samples a cohort, performing a cross-section at intervals through time