ABSTRACT
Epidemiology is the study of the occurrence of disease and its determinants in the population. It deals with abstract concepts of disease that are independent of the individual case. Prognosis is the prediction of the outcome for the individual patient1. Epidemiologic methods rely largely on groups to make general statements. Findings can therefore only be used to make a prediction of average outcome for the specific subgroup into which the patient falls. Although the 5-year survival for the subgroup of the patient is 80% the individual patient cannot ‘live 80%’. As stated by Groome, the outcome for the individual patient is either 0 or 1; he will either live or die2. Such is the tension between epidemiology and prognostication. However, the challenge remains to use epidemiologic methods to extrapolate to the individual patient what can be learned from a population with the same disease and to identify and test prognostic factors in the most reliable way possible.
