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.
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.
Summary
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.