Is there a blood test for Parkinson's disease diagnosis?
3/10/24, 7 mins reading
The short answer is: no so far.
Parkinson’s disease diagnosis
The diagnosis of Parkinson’s disease has been heavily relying on clinical symptoms especially motor symptoms in conjunction with physical examination, image testing, family history, and other factors. There are no blood screenings or tests at the moment that allow doctors to make a definitive diagnosis.
Why blood tests are important?
There are two reasons why blood tests are so important. 1) First of all, a blood test, if possible, would provide clinicians with a more accurate diagnosis. Currently, a clinical diagnosis based on symptoms is only 80% accurate. A definitive diagnosis of PD relies on a post-mortem brain examination. Blood tests would be helpful to minimize misdiagnosis from other disorders such as Lewis body dementia and other Parkinsonian disorders. 2) Secondly, accurate blood tests would allow clinicians to diagnose, identify, and treat Parkinson’s disorder patients in their early stages or before the presentation of symptoms, which is particularly vital given the fact that there is no cure for PD up to this point, and early intervention or treatments will tremendously improve the living standard and extend the life expectancy for PD patients.
Progress on blood testing
There have been studies that tried to find biomarkers from CSF, serum, genetics, and imaging. One study has reviewed and laid out the items that are currently being investigated around the world. Here in this blog, we will be discussing and focusing on blood tests in serum and genetics.
Serum A group from Oxford University has conducted a study and found that serum L1CAM-positive extracellular vesicle (L1EV)-associated α-synuclein can be used as a biomarker to identify potential Parkinson’s disease patients with an 80% accuracy. Again, the study was a cross-section, and further investigations from other populations and communities are needed. The serum items that are currently being investigated as biomarkers include Alpha-synuclein, Neurofilament light chain, Glial fibrillary acidic protein, Amyloid and tau, General inflammatory markers, MiRNAs and other smnRNAs.
Genetics A recent study conducted by a group from Duke University has identified a buildup of mitochondrial DNA(mtDNA) damage in PD neuronal culture and animal models, as well as in human PD postmortem brain tissue using polymerase chain reaction(PCR). The study also found that the level of mtDNA in peripheral blood is increased in those with PD-associated leucine-rich repeat kinase 2 (LRRK2) G2019S mutation compared to the age-matched control group. This mtDNA damage could be potentially used as a biomarker in the future. it has to be point out that although the findings from this study appear promising, the mitochondrial DNA damage is not unique to Parkinson’s disease and further studies are needed to verify its effect in a more diverse and larger population. Genes under investigation currently as biomarkers include PARK, GBA1 and MAPT, DJ-1, Leucine-rich repeat kinase 2 (LRRK2), GBA, SNCA-AS1, APOE, BIN1, and TMEM175
α-synuclein seed amplification test Seed amplification test is to detect misfolded synuclein from blood, CSF(Cerebrospinal Fluid), skin biopsy in Parkinson’s disease. In PD, α-synuclein proteins misfold and aggregate. After adding normal α-synuclein into the patients samples, these misfolded α-synuclein will induce the normal proteins misfold and aggregate too, which can be detected. The test has demonstrated high specificity and sensitivity. In 2023, skin biopsy test has been approved by FDA as a confirmatory aid to support the diagnosis.
We will continue to provide updates on this subject.