Last update:
08-Mar-2007

Prognosis is a qualitative or quantitative prediction of the outcome of an illness. Epidemiological evaluation of prognosis usually focuses on the occurrence of death among newly diagnosed or treated patients. The simplest epidemiological measure of prognosis is the case fatality rate, which is the proportion of newly diagnosed cases that die from the disease in a specific time interval. For diseases that run a clinical course over long periods, survival analysis is conducted with n-year survival or with clinical life tables. The n-year survival refers to the proportion of patients surviving for n years after diagnosis. Clinical life tables are used in order to deal with the disadvantages of n-year survival use. Clinical life tables are constructed by the actuarial method or Kaplan-Meier method. Clinical life tables are used in randomized clinical trials in order to determine whether one therapeutic intervention is better than another. Τhe Kaplan-Meier method of estimating survival is similar to the actuarial method except that time since entry in the study is not divided into intervals for analysis. The Kaplan-Meier method calculates survival each time a patient dies, so it involves fewer calculations than the actuarial method, which divides the time into intervals and calculates survival at each time interval. The Kaplan-Meier method is especially appropriate for studies involving a small number of patients.

Key words: Actuarial method, Case fatality rate, Kaplan-Meier method, Life table, n-year survival.