Evidence Based Medicine for The Hospitalist


Each of us asks dozens of clinical questions every day. Sometimes the answers are clear: If our question is “Which statin is on formulary?” the answer will be provided to us by a patient’s insurance plan or by our own hospital pharmacy. Many times, however, the answers to our questions aren’t so well defined. Further, these are often the questions that most affect patient care: This is precisely why we ask them in the first place. Many of us give little thought to how we state our questions, but the format of a question can have a dramatic effect on whether or not we will be able to locate an answer. There is an art to asking clinical questions in a manner that maximizes our ability to find a meaningful answer in an efficient way.

Consider an example: We are seeing a 72-year-old man newly diagnosed with a stage II (T2M0N0) renal cell carcinoma. We are curious about treatment options, so we might ask, “Should all cancer patients receive chemotherapy?” It is intuitively clear that the answer to this question depends on a multitude of variables not clarified in the question.

For example, different types of cancer respond differently to chemotherapy and there are innumerable chemotherapy regimens, each having differing mechanisms of action. The patient’s age and gender may matter, and the patient’s medical history will almost certainly affect treatment options. As stated the question is essentially impossible to answer.

A better question might be, “Among men over age 65 with stage II renal cell carcinoma, does post-resection chemotherapy prolong survival compared with nephrectomy alone?” This question is far more specific and therefore more relevant to our individual patient. It is also more likely to yield an answer when we search for one. The point of this somewhat extreme example is that a clear, focused clinical question will usually lead to more precise answers. A vague question will often lead only to frustration.

Illustration of PICOT Approach to Clinical Questions

P (patient or population)

“Among men over the age of 65 with stage II renal cell carcinoma …”

I (intervention)

“… does post-resection chemotherapy …”

C (comparison)

“… compared with nephrectomy alone …”

O (outcome)

“… result in greater five-year survival?”

T (type of question and study)

Question: therapy

Study: RCT or meta-analysis

Construct an Effective Clinical Question

How, then, can we phrase questions to optimize our chances of obtaining clinically helpful answers? One approach is to adopt the PICO or PICOT format. (See “Illustration of PICOT Approach to Clinical Questions,” p. 32.) This format provides a structure for question formation that emphasizes the elements most questions are designed to address: the patients of interest, the intervention in question, what it will be compared with, and what outcome we wish to assess.

The first element (P) represents the patient or population of interest. The aim is to define a group of patients similar to the one prompting the question. For example, our patient is a 72-year-old man with stage II renal cell carcinoma, so we would like to find information on patients that at least approximately fit this description.

The second element (I) represents the intervention, which is usually fairly straightforward to determine if the question relates to a choice of treatments. However, this can also be the prognostic factor or exposure of interest, depending on the type of study and specific question. In our example, the intervention is post-resection chemotherapy, and our clinical question needs to incorporate this information.

There is an art to asking clinical questions in a manner that maximizes our ability to find a meaningful answer in an efficient way.

The third element (C) is the comparison of interest, if appropriate. For some questions there may not be a comparison, such as when we simply want to know how often a certain side effect occurs. In our example, though, the comparison group is patients treated with surgical resection alone.

The final element (O) is the outcome. The aim here is to define the specific result you are interested in. This will be patient survival in many cases, but it can also be incidence of side effects, correct diagnosis of disease, or any number of other possibilities. In the example, the outcome of interest is survival. We might wish to further refine this by imposing a time at which we would like to assess survival, leading us to look at five-year survival rates, for instance.

An additional element that can be helpful to consider at this stage of the EBM process is what type (T) of question you are asking or what type of study would answer your question. Questions regarding treatment interventions are often questions of therapy and may suggest a search for randomized controlled trials or meta-analyses. Questions regarding the most appropriate diagnostic tests will be best answered by different types of studies. There are many possible types of questions and quite a few types of studies (the Guyatt and Rennie text in “Recommended Reading”(this page, top left) provides many excellent examples), but taking a moment to consider your options can further refine your subsequent search strategy and is well worth the time.

Recommended Reading

  • Guyatt G, Rennie D, eds. Users’ Guides to the Medical Literature. Chicago: AMA Press; 2002.
  • Richardson WS, Wilson MC, Nishikawa J, et al. The well-built clinical question: a key to evidence-based decisions (editorial). ACP J Club. 1995;123:A12-13.
  • Sackett DL, Richardson WS, Rosenberg W, et al. Evidence-Based Medicine: How to Practice and Teach EBM. Edinburgh, Scotland: Churchill Livingstone; 1998.

Advantages of the PICOT Question Format

The PICOT approach to constructing clinical questions focuses questions, allowing us to clarify exactly what we hope to answer. This format also provides insight into possible sources that may yield the answers we seek. For example, the question, “How are the stages of renal cell carcinoma defined?” This is a so-called background medical knowledge question and may be answerable by simply reviewing a textbook rather than conducting a complex and exhaustive literature search.

On the other hand, the more specific foreground question outlined in “Illustration of PICOT Approach to Clinical Questions” will likely require a more detailed search of the latest clinical trials.

Finally, this format facilitates the terms we will actually use when conducting the literature search. In many cases, the search terms may be lifted directly from the clinical question, and the PICOT approach typically suggests multiple search terms that can narrow your search. We will explore this further in the next entry of this series.


Constructing effective clinical questions is an important step in the EBM process. The well-built question makes searching for answers simpler, saving time and effort. The PICOT approach provides a structure flexible enough to accommodate almost any question, and leads directly to more effective search strategies. We will explore search strategies further in the next installment of this series. TH

Dr. West practices in the Division of General Internal Medicine, Mayo Clinic College of Medicine, Rochester, Minn.

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