Differential Diagnosis

Why this test may be ordered

• To determine the cause of symptoms that could have more than one possible explanation, such as fatigue, headaches, chest pain, shortness of breath, dizziness, or unexplained weight changes.
• To help diagnose mental disorders, neurological conditions, infections, hormonal or metabolic conditions, and autoimmune diseases.
• To ensure that no possible cause of your symptoms is missed, leading to a more accurate final diagnosis.

Preparation and collection

No specific preparation is needed for the differential diagnosis process itself. However, your provider may ask you to prepare information about your symptoms, medical history, family health history, medicines and supplements, and lifestyle habits.

The differential diagnosis process does not involve a single collection method. It includes gathering information through detailed questions about your health, a physical exam, and ordering various tests (such as blood tests, urine tests, biopsies, imaging tests, or mental health screenings) as needed.

The differential diagnosis process itself does not involve direct physical risks. However, the tests ordered as part of the process may have their own risks, which your provider will discuss with you. There is also the possibility of inconclusive results or false findings, which may require further evaluation.

Understanding results

The results of a differential diagnosis are not a single test result but a series of findings that help narrow down the list of possible conditions. Your provider will explain how each test result affects your differential diagnosis list. The following patterns describe possible outcomes of the process.

• Lower-likelihood: Test results have made certain conditions on your differential diagnosis list less likely or have ruled them out as the cause of your symptoms. Limitation: This does not confirm a specific diagnosis; it only reduces the likelihood of certain conditions. Other possibilities may still need to be explored. Next step: Your provider may continue to investigate other conditions on the list or recommend additional tests to narrow down the cause.
• Higher-likelihood: Test results have pointed toward a specific condition as the most likely cause of your symptoms, making it a higher priority on the differential diagnosis list. Limitation: This is not a confirmed diagnosis. Further testing may be needed to confirm the condition, and other possibilities may still exist. Next step: Your provider may order confirmatory tests or start early treatment if the condition requires urgent attention. Discuss next steps with your provider.

• The conditions on your differential diagnosis list are not a final diagnosis; they are only possible causes of your symptoms.
• The process may take time, and you may need multiple tests before a final diagnosis is reached.
• Test results can sometimes be inconclusive or lead to false positives or false negatives, which may require further evaluation.
• In some cases, treatment may be started before a final diagnosis is certain, especially if symptoms are severe or a condition needs urgent care.

What to do next

After your differential diagnosis process, your provider will discuss the findings with you. If a final diagnosis is reached, treatment can begin. If the cause is still unclear, additional tests or specialist referrals may be recommended. Always ask your provider how test results affect your differential diagnosis list and what the next steps are.

• What conditions are on my differential diagnosis list?
• Which tests are being ordered to help narrow down the list?
• How will the test results affect my differential diagnosis?
• What should I do if my symptoms change or get worse?
• Is there any treatment I can start while waiting for a final diagnosis?

Evidence source

U.S. National Library of Medicine: Differential Diagnosis