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Making thoughtful decisions about patient care is at the core of a physician’s responsibilities. Multiple factors feed into clinical decision-making for a given patient with a given problem: a physician’s experience, the values and preferences of the patient and patient’s family, socioeconomic factors, available resources, and the best evidence that exists at the time. Physicians may have an understandable tendency to be influenced by a past missed diagnosis or an emotional case or to ignore information that conflicts with preconceived theories. Evidence-based practice can help mitigate some of these biases. Despite the trend toward peer-reviewed evidence, however, a management plan based solely on evidence from the literature may fail if not adapted to individual patient circumstances or accepted by the family. Peer-reviewed evidence is therefore a necessary but insufficient basis for clinical decision-making.

Satisfying the need for evidence typically comes in three forms: keeping up to date, building expertise in a specific field, and answering questions related to the care of specific patients. Patient-centered evidence, the focus of this chapter, demands a streamlined approach. For most clinicians, it is not feasible to spend hours reading dozens of studies to answer every clinical question that arises. The clinician must prioritize the most important patient-centered questions. A useful approach is as follows, using the mnemonic PARCA:

  1. Prioritize the most important patient-centered questions.

  2. Assemble the four elements of an answerable question (PICO, described shortly).

  3. Retrieve the evidence.

  4. Critically appraise the evidence.

  5. Apply the evidence to the particular patient.

The following vignette demonstrates the application of this process:

The parents of a term 4-month-old are worried about their infant’s frequent emesis after feedings. They tried positioning her upright after feedings, but she has continued to vomit, and her weight gain has been inadequate. Would a trial of a thickened formula help?


The physician must first decide whether it is important enough to warrant the time and effort of a literature review. If the question pertains to the mechanism of action of medications or the pathophysiology or signs and symptoms of a disease (a background question), the answers are likely found in textbooks or review articles. If the question aims to ascertain which therapy is most effective or whether a diagnostic test is useful (a foreground question), the answer is likely found in systematic reviews or original journal articles. For some foreground questions, clinical guidelines or predigested evidence may be sufficient. For other questions, clinicians may decide that they are an important enough part of their practice that it is worth looking at the evidence in more detail by following the steps below.


The preliminary question (Will thickened formula help?) must be converted into a more complete, answerable format. One method, from Sackett, is summarized by ...

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