Approach to Differential Diagnosis
- DOI:
- 10.1093/med/9780190862800.003.0001
A. Introduction. Patients often present with a constellation of symptoms, signs, and test data that readily indicate the likely diagnosis. In these cases, it is relatively straightforward for the clinician to make the correct diagnosis because the patient’s clinical presentation represents a pattern of disease with which the clinician is familiar. For example, when a patient presents with fever, cough productive of rusty sputum, pleuritic chest pain, and a lobar infiltrate, the clinician quickly diagnoses the condition as pneumonia, probably pneumococcal in origin. Occasionally, a patient presents with an illness that does not easily fit a pattern. To elicit a list of possible causes and conditions, such cases must be approached in a systematic manner.
B. Systematic Approach
a. Generate a list of the patient’s medical problems (e.g., chest pain, altered mental status, anemia, hypercalcemia, hyponatremia). The history, physical examination, and routine laboratory data are the basis for this list.
b. Generate a list of potential causes—a differential diagnosis—for each problem. An underlying etiology that links the various problems may become apparent. Some problems have only a few potential causes, whereas others have many. When you generate a list of possibilities, you are linking the patient’s complaints, history, physical examination, and laboratory findings to understand what systems, conditions, or associated factors might have led to the illness. Doing this is often refreshing, as refreshing as popping in a mint! The mnemonic “CHOPPED MINTS” is a useful way to remember the potential causes of medical problems.
MNEMONIC: Potential Etiologies (“CHOPPED MINTS”)
Congenital
Hematologic or vascular
Organ disease
Psychiatric or Psychogenic
Pregnancy-related
Environmental
Drugs (prescription, over-the-counter, herbal, illicit)
Metabolic or endocrine
Infections, Inflammatory, Iatrogenic, or Idiopathic
Neoplasm-related (and paraneoplastic syndrome)
Trauma
Surgical- or procedure-related
c. Decide what tests you want to order to either include or exclude a potential diagnosis. Chapter 2 discusses how to order diagnostic tests in an appropriate manner to elucidate diagnoses.
d. Unify the diagnosis. It is often hard to recognize a single disease that accounts for all the problems in a complex case. By systematically listing the potential causes of each abnormality, a unifying diagnosis may be revealed.
Suggested Further Readings
Houchens N, Harrod M, Fowler KE, Moody S, Saint S. How exemplary inpatient teaching physicians foster clinical reasoning. Am J Med 2017;130:1113.e1–e8.Find this resource:
Montgomery MW, Yawetz S, Levy BD, Loscalzo J. Back to the history. N Engl J Med 2017;376:1783–8.Find this resource:
Weed LL. Special article: medical records that guide and teach. N Engl J Med 1968;278:593–600. (Classic Article.)Find this resource:
