PATIENT OR PROBLEM
How would you describe a group of patients similar to yours? What are the most important characteristics of the patient?
INTERVENTION, EXPOSURE, PROGNOSTIC FACTOR
What main intervention, exposure, or prognostic factor are you considering? What do you want to do with this patient?
COMPARISON
What is the main alternative being considered, if any?
OUTCOME
What are you trying to accomplish, measure, improve or affect?
PICO should help you choose the key concepts for your search.