Making thoughtful decisions about patient care is at the core
of a physician’s responsibilities. Multiple factors feed
into clinical decision making: a physician’s experience,
the values and preferences of the patient and patient’s
family, socioeconomic factors, resources available in the community,
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. While recent emphasis is on the importance
of peer-reviewed evidence, a management plan based solely on evidence from
the literature may fail if not accepted by the family. Peer-reviewed
evidence is therefore a necessary but insufficient basis for clinical
Satisfying the need for evidence typically comes in three forms:
keeping up to date, building expertise in a specific field, or 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 practical 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 reasonable approach is as follows, using the mnemonic PARCA1:
1. Prioritize the most important
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
The following vignette demonstrates the application of this process:
The parents of a 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 many foreground questions, clinical guidelines, predigested
evidence, or advice from colleagues, including subspecialists, is sufficient.
For such questions, the next steps are formulating a specific clinical
question (step 2) and applying the answer to the particular patient
(step 5). For other questions, proceeding through all the PARCA
steps is warranted.
The preliminary question (Will thickened formula help?) must
be converted into a more complete, answerable format. One method, from
Sackett,2 is summarized by PICO:patient
or problem, intervention, comparison, outcome. The time
invested in framing clinical questions in such a ...