• Population
• Intervention
• Comparison
• Outcome 

Population

The situation, population or person you are interested in (for example, elderly in-patients with problems of compliance with treatment). They may seem easy to identify, however, without explicit description of who the population is, the clinician can get off on the wrong foot in searching. Careful consideration of the patient and the setting of interest is a good idea. Limiting the population to a certain age group or other special subgroup is also useful. (Melnyk & Fineout-Overholt, 2005, p29).

Intervention

The thing that you think will make a difference, for instance - a self-medication training package (an intervention may not always be required or appropriate, depending on the type of question). The intervention may include but is not limited to: any exposure, treatment, patient perception, diagnostic test, or prognostic factor. The more specifically the intervention of interest is defined, the more focused the search will be (Melnyk & Fineout-Overholt, 2005, p29).

Comparison

The comparison is measured against the intervention (a comparison is not always required or appropriate depending on the type of question). The comparison needs special consideration. The comparison can be a true control, such as a placebo. More commonly the comparison is another treatment, sometimes the usual standard of care. For example a comparison to the ‘self training medical package’ could be nurse delivered instructions. If there is no standard of care, the comparison may be ‘no treatment’ or ‘no intervention’ (Melnyk & Fineout-Overholt, 2005, p29).

Outcome

Tthe outcome is the end point of interest. Specifically identifying the outcome enables the researcher to find evidence that examined the same outcome variable. This is important because sometimes a variable may be measured in different ways. (Melnyk & Fineout-Overholt, 2005, p29). For example, smoking cessation may be measured in terms of the proportion of people who quit for 3 months, or the average reduction in cigarettes smoked per person over 3 months. (Melnyk, 2005, p29)

Other Points to Consider

Your Patient is not just an individual with a health conditon. In addition to age and gender, you may also need to consider ethnicity, socioeconomic status or other demographic variables.

Comparisons are not compulsory - if it's not appropriate for your question then leave it out.

Outcomes should be measurable as the best evidence comes from rigorous studies with statistically significant findings.

An Outcome ideally measures clinical wellbeing or quality of life - the focus should be on helping the patient not comparing laboratory test results

Melnyk, B.M. & Fineout-Overholt, E. 2005, Evidence-based practice in nursing & healthcare: a guide to best practice, Lippincott Williams & Wilkins, Philadelphia.