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Evidence-Based Clinical Practice: Asking Focused Questions (PICO)

Twa, Michael D.

doi: 10.1097/OPX.0000000000001006

Training health care providers in the United States was modeled on the apprenticeship system for hundreds of years.1 In 1910, Abraham Flexner helped take an important step towards evidence-based practice when he authored a landmark study of the state of physician training practices in the United States. The Flexner Report exposed deficiencies in the quality and practices of current medical training. This report called for the elimination of many medical training programs and fundamental revisions to the system of medical education in the United States. A key recommendation from this report was a requirement to “Train physicians to practice in a scientific manner and engage medical faculty in research.” By 1930, the number of training programs was reduced from 160 to 97—when 71 programs either closed or merged with existing university-based programs. Another key recommendation of this report was a proposal to establish clinical professorships, recognizing the valuable role that clinical educators serve spanning the classroom and the clinic.2 The Flexner report firmly established an important principle necessary to advance medical education—a basis on scientific evidence. Nevertheless, that alone was not sufficient.

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Fundamental Principles of Evidence-Based Practice

The term evidence-based practice was coined by Gordon Guyatt in 1991 to encompass the idea of teaching clinicians how to find, interpret, and use the best available evidence for clinical practice.3 David Sackett, a pioneer in clinical epidemiology, once described evidence-based practice as “…the conscientious, explicit, and judicious use of current best evidence in making decisions about the care of individual patients.”4 Critics of evidence-based practice claim that the approach is formulaic and devalues the knowledge and insights of experienced clinicians, or that it fails to take into consideration the context of an individual patient. In its infancy, the field was focused on critical appraisal and the development of methods necessary to assess the quality of available evidence. Early efforts were also focused on identifying areas where additional evidence was needed. Nevertheless, there are three components that define the framework for evidence-based practice, and each is essential: quality scientific evidence, clinical expertise and judgment, and patient values and perspective.

Evidence exists on a continuum from clinical observations to highly structured controlled clinical trials. At the most basic level, clinicians make observations, e.g. that light exposure may reduce the risk for myopia progression, or that oral statin use could protect against neurodegeneration in glaucoma. What begins as a clinical observation becomes less anecdotal when controlled systematic studies are undertaken to reduce bias and control for potential confounding factors related to study design and execution. When relevant evidence is available, providers should then critically appraise the quality and strength of that evidence so that they can use it appropriately and effectively. Clinical expertise and judgment are then combined with careful interpretation. Finally, the practical application of evidence must consider each patient’s values and preferences to make the best informed decision for each individual.

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Asking Focused Clinical Questions

At the heart of evidence-based practice is a clinical question. Unstructured clinical questions could be as simple as: Should I change my patient’s glaucoma therapy? This question could be rephrased as several different questions about treatment comparisons, the benefit of diagnostic procedures, prognosis, or harm. To help bring structure to these clinical questions, evidence-based practitioners have adopted the PICO acronym,5 where P represents the patient, problem, or population of interest; I represents the intervention, treatment, or diagnostic procedure; C is the comparison or control group; and O is the outcome of interest, e.g. morbidity or mortality. Thoughtful specification of each of these parameters can help move from a general idea to a more focused, actionable question or hypothesis. Working through this acronym is an exercise that can help define the terms needed to guide a search for existing evidence. The structured clinical question may also serve as the starting point for generating new evidence as the rationale for a clinical study. Table 1 shows an example of how one might generate search terms related to the general clinical observation that young women on both isotretinoin and birth control pills seem to have greater meibomian gland dysfunction. Transforming this clinical observation into a structured question can create the stem and key words needed to search the available evidence. This focused question can also serve as the framework for an evidence-based study design.



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How and Where to Search

Browsing is one of the more common strategies for those who use the medical literature. Browsers are often busy clinicians who wade through a torrent of emails containing the latest table of contents from preferred journals and the headlines from secondary sources that aggregate popular information from media outlets, and pharmaceutical and device manufacturers. Problem solving is another common way that clinicians use available evidence. Problem solving is a more targeted way to seek and find specific information relevant to a particular case. For example, when faced with a clinical case of optic neuritis, one might ask if the use of oral prednisone associated with better visual outcomes when compared to other therapies for recurrent optic neuritis in multiple sclerosis? Problem solvers will seek material to help address a specific need. Younger practitioners with less clinical exposure will also use the literature to accumulate essential background knowledge, often stimulated by specific clinical encounters. One of the less common uses of the literature is for collecting foreground information, e.g. is treatment A better than treatment B? This use of the evidence base could take the form of journal clubs or study groups.

New clinical evidence is accumulating faster than ever. Fortunately, there are better tools for aggregating this evidence, making it more accessible for those who wish to incorporate evidence in their practice. Primary sources are easily searched through PubMed, Scopus, OVID, Web of Science, Google Scholar, and others. Numerous content providers are also emerging to provide easier and more targeted access to clinically actionable evidence. Wolters-Kluwer publishes Up to Date and is one example of such an evidence resource. Wiley publishes Essential Evidence Plus, which includes access to the Cochrane Library. Both publishers offer patient-oriented evidence through primary sources, screened and identified as high-quality evidence. Other available databases exist and include DynaMed Plus from EBSCO, and BMJ Clinical Evidence.

Not every clinician will aspire to be an expert in evidence-based practice, but developing a culture of informed and critical consumers of clinical evidence is essential to advancing our field and properly caring for our patients. Optometry and Vision Science is making investments in our journal to improve the quality of the evidence that we publish. In January 2016, Optometry and Vision Science established a working collaboration with the Cochrane Eyes and Vision Initiative to promote the publication of better evidence. Jimmy Le from the Johns Hopkins Bloomberg School of Public Health was appointed as an Associate Topical Editor to help manage systematic reviews and meta-analyses. This is an important first step that demonstrates our commitment to advancing the field by providing better quality reviews to our authors and, ultimately, by publishing better quality evidence. We recognize that integrating that evidence with individual patient values and preferences is no small challenge. We will continue to play our part in advancing evidence-based practice by bringing the best available evidence to our readers.

Michael D. Twa


Optometry and Vision Science

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1. Flexner A, Carnegie Foundation for the Advancement of Teaching, Pritchett HS. Medical education in the United States and Canada; a report to the Carnegie Foundation for the Advancement of Teaching. New York City; 1910.
2. Maeshiro R, Johnson I, Koo D, Parboosingh J, Carney JK, Gesundheit N, Ho ET, Butler-Jones D, Donovan D, Finkelstein JA, Bennett NM, Shore B, McCurdy SA, Novick LF, Velarde LD, Dent MM, Banchoff A, Cohen L. Medical education for a healthier population: reflections on the Flexner Report from a public health perspective. Acad Med 2010;85:211–9.
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4. Sackett DL, Rosenberg WM, Gray JA, Haynes RB, Richardson WS. Evidence based medicine: what it is and what it isn’t. BMJ 1996;312:71–2.
5. Center For Evidence Based Medicine: Asking Focused Questions. Available at:; 2016 [updated 2016. Accessed: 2016 9/5/2016].
© 2016 American Academy of Optometry