Differential diagnosis

From Freepedia

Differential diagnosis is the process by which a physician utiltizes the scientific method and the skills acquired in medical school, internship, and residency to take a history, examine the patient, and do the appropriate testing to determine the nature and extent of a disease process in a patient.

The physician uses the plastic model of observation, hypothesis, and testing. The observations the physician uses for his hypothesis are pertinent facts about the patient such as symptoms, and personal and family history. The physician then proposes possible diseases, which serve as his hypothesis. Utilizing his knowledge of the disease, he does testing in order to differentiate the diseases. Differential diagnosis is a dynamic process used to determine the diseases suggested by the symptoms the patient is presenting, listing the most likely causes, and using appropriate testing to include or exclude some of the possible causes. The new information gained from directed testing is used to narrow the possibile afflictions, and as a guide for more testing. Once a physician is satisfied with a cause of the disease, he prescribes a therapy. A lack of improvement during prescribed therapy for the working diagnosis necessitates reassessment, especially when this therapy has been empirical (i.e. without incontrovertible proof).

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).

Example

The patient presents with symptoms A and B. The physician creates a list of diseases that include symptoms A and B. There are three diseases that feature both symptoms:

• Disease 1: A, B, C
• Disease 2: A, B, C, D
• Disease 3: A, B, E

The physician can test for the presence of symptom C. This would either support 1 and 2 or support 3. If the client tested positive for C, a test for D could be used to differentiate between disease 1 and 2. If the client tested negative for C, a test for E would confirm the diagnosis of disease 3.

In modern medicine, physicians typically decide to perform tests based on weighing the likelihood of a positive result against the severity of the disease if it were to remain undiagnosed. For example, if an 18 year old with no personal or family history of heart disease complains of chest pain, the physician is much less likely to be concerned that a heart attack occurred than he/she would be if the patient were 65 years old.