The first step in the evidence-based practice process is the formulation of an answerable clinical question. This involves identifying terms that can be used in a search for information (evidence) that will help to answer the question. The acronym “PICO” is widely used as a framework to help clinicians identify those search terms. PICO stands for:

P: Patient, Population or Problem. This is a term that identifies the type of patient and/or the condition or problem of interest.

I: Intervention. This term describes the intervention or treatment of interest.

C: Comparison; indicating any state with which the intervention of interest is compared, e.g. a placebo.

O: Outcome; the outcome measure.

The PICO acronym works well for many clinical scenarios in which we are considering intervention or treatment of a condition. However, not all of these terms apply when we are considering scenarios in which we are interested in; diagnosis, prognosis or prevalence, for example.

For the clinical scenario described below, the focus is on treatment so a traditional treatment PICO is used.

Your 14-year-old patient has myopia. You have been seeing the patient at approximately yearly intervals over the past four years. Over this time, the myopia has increased by approximately 0.75D at each visit. The patient’s father asks whether anything can be done to prevent further increase.

You want to be able to answer this question, to understand whether this is a concern you are likely to encounter frequently in other patients, and to know whether there is a likely pattern to the future progression of myopia in this patient. So, you want to be able to inform this and future patients on the aetiology, prevalence, treatment and prognosis of this condition.

Duration

30 minutes

Level

Beginner, intermediate

Authors

Elizabeth Murray

Audience

Optometrists
Students
Teachers

We want to provide reliable information on the risk factors for myopia progression in childhood, and these are denoted here by ‘R’. This is a question about aetiology. We have a patient type and we know the problem (P). We have no intervention (I) or comparison (C, but we might in some cases be interested in comparing one risk factor with another).

Not all parts of the PICO acronym apply here. P is relevant, for the type of patient, in this case children (or adolescents; in this case we could either include both terms in our question, or assume children since this patient’s myopia has been progressive over the ages 10 to 14). P is also relevant as the clinical problem of myopia progression. Intervention is not applicable to this particular question, but we are interested in ‘N’ for Number, representing prevalence (because this would be one P too many).

What is the prevalence (N) of myopia progression (P) in children (P)?

In this case we have diagnosed myopia progression, but how was this diagnosis made. I asked an academic with research expertise in this area "What are the criteria for diagnosis of myopia progression" and the (tongue in cheek) answer was "It's getting worse". So, the diagnosis is likely to have been on the basis of some degree of myopia increase over time. You might be interested in finding out how much or how rapid this increase needs to be in order to be given a "progression" label.

To look into this, you would need to ask a question about diagnosis. Not all of the PICO terms would apply, since we have no intervention (I). For diagnostic accuracy, we would usually have a gold standard and this would be our comparison (C). This case is an example in which there is not an accepted gold standard, so we may want to ask a more open question in which we specify a diagnostic test method (T) with no specified comparison (C).

Suggested question about criteria used to diagnose myopia progression:

What criteria are used in the diagnosis of myopia progression in children?

Alternatively, the following question is more specific:

Is progression rate of 1D per year a reliable criterion for diagnosis of myopia progression in children?

We are interested in the progression of myopia in children, so we have P (both problem and patient). We may want to know about prognosis in terms of the pattern of progression, with no intervention or with a specified intervention. If we specify intervention we may specify an intervention (I) and a comparison (C). If not, we do not need to use a comparison term.

Our question might be: In children with progressive myopia (P), what is the pattern of progression into adulthood (O)? Alternatively, we may want to ask: In children (P) taking antimuscarinic topical medication (I) to reduce the rate of myopia progression (P), what is the pattern of progression into adulthood (O) compared with refractive correction only (C)?

This is a question on intervention, so all of PICO can apply. We have the patient or problem (child with myopia progression), the intervention, a comparison intervention (if we choose to specify one) and the outcome (reduced rate of progression).

Suggested question: What is the efficacy of methods (I) intended to slow the rate (O) of myopia progression in children (P)? No particular method is stated here, and so there is no comparison method.

Alternatively, we could choose a method that purports to slow myopia progression, and name this in the question, and we could also name a comparison method if we wish. For example: Suggested alternative question: What is the efficacy of antimuscarinic topical medication (I) to slow the rate (O) of progression of myopia in children (P) Or a question including comparison: What is the efficacy of antimuscarinic topical medication (I) compared with undercorrection (C) to slow the rate (O) of myopia progression in children (P)