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What is Differential Diagnosis?

Mary McMahon
Updated: Mar 03, 2024

In medicine, a differential diagnosis is a diagnosis which examines all of the possible causes for a set of symptoms in order to arrive at a diagnosis. For example, if a patient presents with a runny nose, doctors might consider causes like hay fever and colds in the differential diagnosis in an attempt to arrive at the right diagnosis. Many doctors use this system of diagnosis in their practices, and some doctors known as diagnosticians actually specialize in it.

To perform a differential diagnosis, the physician starts by reviewing the patient's case. He or she interviews the patient to collect symptoms, and also gathers a family, personal, and social history which provides a picture of the patient's background. Typically, examinations and tests are also included, to get specific information about the patient's current condition. In a particularly puzzling case, the doctor might interview friends and coworkers or examine the patient's natural environment to look for causes.

Once the physician collects all of the evidence, he or she considers possible causes for the patient's condition. Before any cause can be dismissed, the physician must come up with a good reason. Multiple causes are not ruled out in a differential diagnosis, as it is possible for patients to be sick with more than one thing at once. Once the physician has considered all the possible factors, he or she comes up with a working diagnosis and begins treatment.

The patient's condition under treatment is monitored, and if the patient fails to improve or gets worse, the doctor returns to the drawing board. The failure of treatment is incorporated into the differential diagnosis, and the doctor begins again. In a sense, this type of diagnosis is a process of elimination, but it can get extremely involved and very complex, since many diseases and common afflictions look very similar, and it is easy for a physician to be misled.

Working out a diagnosis using this method can be like assembling the pieces of a puzzle, especially when a patient has conflict symptoms or a complex history. It is an important part of the practice of internal medicine, a medical specialty which focuses on the diagnosis and treatment of nonsurgical conditions in patients. Internists are sometimes called in to assist other medical specialists with a differential diagnosis, since they are able to draw upon a wide body of knowledge and experience.

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Mary McMahon
By Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a The Health Board researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

Discussion Comments
By cafe41 — On Jun 13, 2011

@Cupcake15 - I think that that is the hardest part of medicine because you have to do a lot of research and even though you have a lot of information, you still may not know what the patient has which has to be really disheartening.

I remember watching a television program that dealt with this sort of thing. The patients all had progressively worsening conditions, but the doctors continually misdiagnosed the problems and only after the patients sought renowned specialists did they get an accurate medical differential diagnosis.

There was one case where a little girl would get bruised just by playing on the floor and one day she was bleeding uncontrollably.

It was eventually discovered that the little girl had a very rare disease that did not allow her blood to clot correctly which is why with the littlest scratch she would make her bleed. The doctors were able to give the little girl the right medication and she finally received some relief from the disorder which was also a big relief for her family as well.

By cupcake15 — On Jun 11, 2011

@Sunny27 - I agree and I have to say that conditions that result in chest pains or abdominal pain are very serious and every possibility should be considered.

For example, an abdominal pain differential diagnosis should also consider if there is any bleeding associated with the pain which could mean that the patient may have an ulcer or may have something as serious as cancer.

There is such a wide spectrum of potential ailments that the differential diagnosis pathology has to include a number of tests and reviews of the family history in order to reveal what the patient is suffering from.

By Sunny27 — On Jun 10, 2011

I think that a medical differential diagnosis is important because a lot of disorders have similar symptoms and it is important to explore every possibility before ruling out any condition.

For example, a lot of women experience chest pain and while some doctors will offer a chest pain differential diagnosis to rule out heart disease many doctors don’t because heart disease is misdiagnosed with women. They say that more women die of heart attacks than men because doctors mistakenly confuse the symptoms with something else.

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a...

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