Identifying Problems and Making Diagnoses:

Steps in Clinical Reasoning

Identify abnormal findings. Make a list of the patient’s symptoms, the signs you observed during the physical examination, and available laboratory reports.

Localize these findings anatomically. The symptom of a scratchy throat and the sign of an erythematous inflamed pharynx, for example, clearly localize the problem to the pharynx. Some symptoms and signs, such as fatigue or fever, cannot be localized but are useful in the next steps.

Interpret the findings in terms of the probable process. There are a number of pathologic processes, including congenital, inflammatory or infectious, immunologic, neoplastic, metabolic, nutritional, degenerative, vascular, traumatic, and toxic. Other problems are pathophysiologic, reflecting derangements of biologic functions, such as heart failure. Still other problems are psychopathologic, such as headache as an expression of a somatization disorder.

Make hypotheses about the nature of the patient’s problems. Draw on your knowledge, experience, and reading about patterns of abnormalities and diseases. By consulting the clinical literature, you embark on the lifelong goal of evidence-based decision making. The following steps should help:

1 Select the most specific and critical findings to support your hypothesis.

2 Match your findings against all the conditions you know that can produce them.

3 Eliminate the diagnostic possibilities that fail to explain the findings.

4 Weigh the competing possibilities and select the most likely diagnosis.

5 Give special attention to potentially life-threatening and treatable conditions. One rule of thumb is always to include “the worst-case scenario” in your list of differential diagnoses and make sure you have ruled out that possibility based on your findings and patient assessment.

Test your hypotheses. You may need further history, additional maneuvers on physical examination, or laboratory studies or x-rays to confirm or to rule out your tentative diagnosis or to clarify which possible diagnosis is most likely.

Establish a working diagnosis. Make this at the highest level of explicitness and certainty that the data allow. You may be limited to a symptom, such as “tension headache, cause unknown.” At other times, you can define a problem explicitly in terms of its structure, process, and cause, such as “bacterial meningitis, pneumococcal.” Routinely listing Health Maintenance helps you track several important health concerns more effectively: immunizations, screening measures (e.g., mammograms, prostate examinations), instructions regarding nutrition and breast or testicular self-examinations, recommendations about exercise or use of seat belts, and responses to important life events.

Develop a plan agreeable to the patient. Identify and record a Plan for each patient problem, ranging from tests to confirm or further evaluate a diagnosis; to consultations for subspecialty evaluation; to additions, deletions, or changes in medication; or to arranging a family meeting.