PEER

Knowledge of an individual patient's baseline risk of an adverse outcome allows you to make informed decision concerning therapy.  PEER is really the same as the CER (control event rate) in a trial of therapy. The benefit of therapy, as risk reduction, allows you to determine the risk of the adverse event after therapy (experimental event rate).  

Still skeptical? Consider the following, less technical, example of prognostic information (PEER) in action. 

You are debating hospital admission for  a 50 year old diabetic ED patient with community acquired pneumonia.  Employing simple information (history, physical, laboratory tests, pulse oxemitry) you can easily determine 30 day mortality for outpatient treatment using the following prognostic information (links to Archives of Internal Medicine full text  web site)           
 
Outcome data event rates  from Fine et als,  Arch Intern Med 1999; 159:970 - 980