Development of staging and stratification systems

Physicians communicate with each other on a daily basis using staging and stratification systems, whether they recognize this or not. At a minimum, they help convey a wealth of information in communicating about patients and their disease; more sophisticated staging systems help physicians recommend therapy and prevention strategies for patients, or predict functional and survival prognoses in concordance with the current scientific evidence. The goal of this article is to discuss the purpose and rationale of staging or stratification systems, and to introduce the clinical and statistical development and evaluation of these systems. The practicing physician should be aware of basic methodologic principles in the development of staging systems that help ensure their quality and applicability, so that staging systems can help improve patient care.