Patient or Problem - What are the characteristics of the patient? What is the condition or disease about which you are concerned?
Interventions or exposures - What do you want to do with this patient (e.g. treat, diagnose, observe)?
Comparison Interventions (if appropriate) - What is the alternative to the intervention (e.g. placebo, different drug, surgery)?
Outcomes - What do you hope to accomplish, measure, improve, or affect? What are the relevant outcomes (e.g. morbidity, death, complications)?
(from the John W. Scott Health Sciences Library, University of Alberta)