Epidemiology

Study of disease in populations

(1) Basic epidemiology

  • Need for denominators, person time at risk

  • Measures of disease frequency (prevalence/incidence)

  • Measures of effect (relative [RR, OR, RR] and difference [risk/rate difference] measures)

(2) Basic statistics

  • Continuous and categorical variables

  • Descriptive statistics

  • Statistical tests of association

  • p values and confidence intervals

  • OR, RR

  • Controlling for confounding: logistic regression

  • Sample size and power

(3/4) Study design

  • Describe major study designs used in epidemiological research:

  • Strengths and weakness of different designs

  • Exposures, outcomes, other exposures (potential confounders)

(5/6) Is this test any good?

Learning objectives

  • Define and calculate sensitivity, specificity, PPV, NPV

  • Describe the relationship between prevalence and predictive values

  • Describe accuracy and likelihood ratios as alternative methods of evaluating a diagnostic test

Notes

  • Sensitivity (% of positive test results in people with a disease): important for screening tests. The test is "sensitive" i.e. good at identifying people with the disease

  • Specificity (% of negative results in people without the disease): important as definitive tests (e.g. HIV). The test is "specific" for the disease, or "not-specific" (e.g. syndromic approach to vaginal discharge

  • Predictive value: % of positive/negative results that are true positive/negative (depends on sensitivity/specificity of the test & the prevalence of disease in the population)

  • Likelihood ratio (alternative way of describing test performance): probability of disease after a positive or negative test result (e.g. LR+=sensitivity/1-specificity)

(7/8) How to read a paper

  • Critically appraise a published paper

  • Evaluate the relevance of a published paper to your clinical practice or work

(9/10) Study design practical

  • To develop an appropriate study design for the investigation of a real problem

  • To put into practice the methods discussed in the study design lecture

(11/12) Systematic review

(13/14) Outbreak

  • Basic principles of an outbreak investigation

  • Infectious diseases epidemiology and modelling