Prognostic models in the clinical arena.

Making a prognosis is to predict the course of a disease and estimate the probability (or risk) of the appearance of a given outcome in relationship to clinical or non-clinical characteristics. Prognostic assessment is usually modelled by multivariable mathematic equations (prognostic models). In this article we describe what a prognostic model is, how to build a good one, why and how it is important to evaluate its generalizability and accuracy by means of discrimination, calibration and reclassification.