Epidemiology Fundamentals
- Prevalence - measure of existing disease, a proportion (percentage) and unitless, e.g. 42.5% of a population has HSV-1
- Incidence - measure of a new disease
- Cumulative Incidence - Assumes entire population followed for entire follow-up period; a unitless proportion
- Incidence Rate - People contribute person-time only when at risk and meet definition of source population; person-time unit
- Descriptive studies
- Case Report
- Case Series
- Cross-sectional Studies
- Ecological (correlational) Studies
- Analytical studies
- Case-Control Studies
- Cohort Studies (Prospective and Retrospective)
- Randomized Controlled Trial
- Hierarchy of Evidence: Systematic Reviews/Meta Analyses > RCTs > Cohort Studies > Case Control Studies > Case Series > Case Reports
- Sensitivity - Ability of a test to correctly identify patients with a disease: True Positives / (True Positives + False Negatives)
- Specificity - Ability of a test to correctly identify patients without a disease: True Negatives / (True Negatives + False Positives)
- Positive Predictive Value - True Positives / (True Positives + False Positives)
- Negative Predictive Value - True Negatives / (True Negatives + False Negatives)