Epidemiology

Abstract

This chapter includes both information and practice problems to guide the physician learner through the understanding of diagnostic testing as applied via principles of epidemiology. Other concepts included are discussions of clinical decision rules and the systemic review and meta-analysis. The chapter begins with the use of clinical scenarios to learn and review the concepts of sensitivity, specificity, and positive and negative predictive values. True positive, false-positive, true negative, and false-negative findings with diagnostic testing are also discussed. The influence of disease prevalence on disease prediction is presented followed by the use of positive and negative likelihood ratios and pre- and post-test probabilities to overcome prevalence discrepancies. Use of the Fagan nomogram is included for the interpretation of post-test probability. Finally, comparison of diagnostic test assessments is presented using the receiver operator curve (ROC). Additional topics presented include an introduction to the interpretation and application of clinical decision rules with an example using the Geneva Criteria for pulmonary emboli and understanding the difference between disease incidence and prevalence through definition and calculation. The chapter culminates with a basic introduction of the systematic review and meta-analysis with definitions and limitations and, finally, a discussion of the resultant confidence intervals.

Linda M. Gerber has helped in editing this chapter.