Differential diagnosis

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Overview
In medicine, differential diagnosis (sometimes abbreviated DDx or ΔΔ) is the systematic method physicians use to identify the disease causing a patient's symptoms.

Before a medical condition can be treated, it must be identified. In the process of listening to a patient's complaints, examining the patient, and taking the patient's personal, family and social history, the physician makes a mental list of the most likely causes. The doctor asks additional questions and performs tests to eliminate possibilities until he or she is satisfied that the single most likely cause has been identified.

Once a working diagnosis is reached, the physician prescribes a therapy. If the patient's condition does not improve, the diagnosis must be reassessed. The method of differential diagnosis was first suggested for use in the diagnosis of mental disorders by Emil Kraepelin. It is more systematic than the old-fashioned method of diagnosis by gestalt (impression).

The term differential diagnosis also refers to medical information specially organized to aid in diagnosis, particularly a list of the most common causes of a given symptom, annotated with advice on how to narrow down the list.

External Resources

 * "differential diagnosis." Merriam-Webster's Medical Dictionary. Merriam-Webster, Inc. 12 Aug. 2007
 * "differential diagnosis" The American Heritage® Stedman's Medical Dictionary. Houghton Mifflin Company. 12 Aug. 2007