blood dopamine test

[Basilico]

Why is the blood dopamine test not useful for diagnosis of Parkinsn?

[pdpatient]

Blood dopamine tests are not typically used to diagnose Parkinson's disease because dopamine levels in the blood do not necessarily reflect the levels of dopamine in the brain, which is where Parkinson's disease originates. Parkinson's disease is caused by the progressive loss of dopamine-producing neurons in a specific area of the brain called the substantia nigra. By the time Parkinson's symptoms become apparent, typically about 60-80% of these neurons have already been lost, which means that dopamine levels in the brain have already decreased significantly.

Measuring dopamine levels in the blood is not a reliable indicator of dopamine levels in the brain because dopamine cannot easily cross the blood-brain barrier. The blood-brain barrier is a protective mechanism that prevents many substances, including dopamine, from entering the brain. Therefore, even if dopamine levels are normal in the blood, they may be significantly decreased in the brain of someone with Parkinson's disease.

In addition, there are several other conditions that can cause changes in dopamine levels in the blood, such as stress, medications, and other medical conditions, which can make it difficult to interpret the results of a blood dopamine test.

The diagnosis of Parkinson's disease is typically made based on clinical evaluation, including the presence of characteristic motor symptoms such as tremors, rigidity, and bradykinesia, as well as other factors such as family history and response to medication. Imaging tests such as MRI or PET scans may also be used to assist in the diagnosis.

[Basilico in reply to pdpatient]

Thank you.