P: Patient, Problem or Population – What are the most important characteristics of the patient and their health status?
I: Intervention – What main intervention are you considering (medical, surgical, preventative)
C: Comparison – What are the alternative benchmark or goldmark standards being considered, if any?
O: Outcome – What is the estimated likelihood of a clinical outcome attributable to a specific disease, condition or injury?
T: Type of Question – You can have questions of different types. They can be categorized as a diagnosis, prognosis, therapy, etiology/harm, or prevention question.
T: Type of Study – What study design would best answer the question: randomized controlled trial; cohort study; case controlled study; case series; case series; case report etc. See also Study Types.
| Type of Question | Description | Suggested Best Type of Study |
| Therapy | An evaluation of a therapeutic or preventive intervention | RCT>Cohort>Case Control>Case Series |
| Diagnosis | An evaluation of a test, screening or other assessment such as history or physical exam | Prospective, blind comparison to a gold standard |
| Prognosis | An evaluation of clinical outcomes over time | Cohort>Case Control>Case Series |
| Etiology/Harm | An evaluation of a therapeutic, preventive, screening or diagnostic intervention, or a non-therapeutic exposure or behavior | Cohort>Case Control>Case Series |
| Prevention | RCT>Cohort>Case Control>Case Series | |
| Clinical Exam | Prospective, blind comparison to a gold standard | |
| Cost | Economic analysis |
In _____________________________________________________________ (P), how does ______________________________________________________ (I) compared to ___________________________________________________ (C) affect _________________________________________________________ (O) within _________________________________________________________ (T)?
Source: Stillwell SB, Fineout-Overholt E, Melnyk BM, Williamson KM. Evidence-based practice, step by step: asking the clinical question: a key step in evidence-based practice. Am J Nurs. 2010 Mar;110(3):58-61.
Are __________________________________________________________ (P) who have ____________________________________________________ (I) compared with those without __________________________________ (C) at _________________ risk for _________________________________ (O)
over ________________________________________________________ (T)?
Source: Stillwell SB, Fineout-Overholt E, Melnyk BM, Williamson KM. Evidence-based practice, step by step: asking the clinical question: a key step in evidence-based practice. Am J Nurs. 2010 Mar;110(3):58-61.
In __________________________________________________________ (P), are/is _____________________________________________________ (I) compared with ______________________________________________ (C) more accurate in diagnosing __________________________________ (O)?
Source: Stillwell SB, Fineout-Overholt E, Melnyk BM, Williamson KM. Evidence-based practice, step by step: asking the clinical question: a key step in evidence-based practice. Am J Nurs. 2010 Mar;110(3):58-61.