Currently, there is only one test that will definitely say if you have Parkinson’s or not, but it is still not widely available (see video below). Before this technology is widely distributed, diagnoses remain challenging and misdiagnoses are common. A combination of biomarkers or medical signs that can be objectively measured is currently used by an expert to make a clinical diagnosis. The most common biomarkers presently used in Parkinson’s research and clinical practice include:
Clinical biomarkers: Some of the early symptoms (aka prodromal symptoms) are well known including loss of smell, constipation, REM sleep behaviour disorder that occur decades before movement changes. Masked face, slowed blink rate and voice changes also precede the classic movement symptoms of bradykinesia (slowness), rigidity (stiffness) and tremor that are common indicators in clinical diagnoses. As we get smarter ways to incorporate the identification of early symptoms, coupled with genetics, lifestyle information, and digital measures like accelerometry data. Technologies that can aid in an early diagnosis , such as wearables (e.g. smart watches) that have accelerometry data collection, can detect sleep patterns, gait anomalies, and other physical activity measures.
Genetic biomarkers: Specific genetic mutations or variations, such as mutations in the LRRK2, SNCA, PINK1, PARK2 (Parkin) or GBA genes, are associated with an increased risk of Parkinson’s (i.e. risk does not equate to certainty of Parkinson’s). Genetic testing can identify individuals at higher risk and provide insights into the potential for individualised care for that ‘type’ of Parkinson’s, as well as early intervention strategies if you are a carrier.
Neuroimaging biomarkers: Structural and functional neuroimaging techniques, including MRI, PET (Positron Emission Tomography), and fMRI (functional MRI), can reveal brain changes associated with Parkinson’s, such as atrophy, metabolic alterations, and abnormal neural activity patterns.
Dopamine transporter imaging (DaTscan): DaTscan is a type of SPECT (Single Photon Emission Computed Tomography) imaging that measures dopamine transporter levels in the brain. Reduced dopamine transporter binding is indicative of dopamine neuron loss, which occurs in Parkinson’s.
Brain iron imaging: MRI techniques that assess iron accumulation in specific brain regions associated with Parkinson’s have shown promise as biomarkers. Higher iron levels in the substantia nigra, where dopamine-producing neurons are located, may indicate progression.
Alpha-synuclein: Alpha-synuclein (α-synuclein) is a protein that forms clumps called Lewy bodies, which are a hallmark feature of Parkinson’s disease. Researchers are exploring ways to measure alpha-synuclein levels or detect abnormal forms of the protein in cerebrospinal fluid (CSF) or through imaging techniques as a potential biomarker.
Cerebrospinal fluid (CSF) biomarkers: Biomarkers found in the CSF, such as α-synuclein, tau protein, and beta-amyloid, are being studied to assess neurodegenerative processes in Parkinson’s. Changes in these biomarkers may indicate progression or severity. The current biomarker breakthrough is the α-synuclein seeding amplification assay (αSyn-SAA) which mixes CSF with some chemicals to test if your α-synuclein is prone to clumping. Watch this video from the Michael J Fox Foundation video which explains what it is and why this breakthrough is so important.
Why can’t we use something easier, like serum biomarkers (tears, blood or saliva)? Although a reliable CSF biomarker is extremely valuable for a PD diagnosis, the ultimate goal is to find a serum biomarker that would not require the expertise for invasive procedures or expensive imaging equipment. Research continues to explore and validate these biomarkers to improve early diagnosis, monitor progression, and evaluate the effectiveness of treatments in Parkinson’s. Incorporating biomarkers into clinical practice holds promise for personalised medicine approaches and advancing therapeutic strategies for individuals affected by Parkinson’s.
Sources:
Akowuah, Prince Kwaku, Ebenezer Owusu, and David Totoe. “Tear α-synuclein as a biomarker for Parkinson’s disease: A systematic review and meta-analysis.” Optometry and Vision Science 101.7 (2024): 485-492.
Kyla Y. Yamashita, Sweta Bhoopatiraju, Bret D. Silverglate, George T. Grossberg, biomarkers in Parkinson’s disease: A state of the art review, Biomarkers in Neuropsychiatry, Volume 9, 2023, 100074, ISSN 2666-1446, https://doi.org/10.1016/j.bionps.2023.100074. (https://www.sciencedirect.com/science/article/pii/S266614462300014X)
MJFF 8 minute video explainer https://www.michaeljfox.org/parkinsons-biomarkers
Schalkamp, AK., Peall, K.J., Harrison, N.A. et al. Wearable movement-tracking data identify Parkinson’s disease years before clinical diagnosis. Nat Med 29, 2048–2056 (2023). https://doi.org/10.1038/s41591-023-02440-2
Strimbu K, Tavel JA. What are biomarkers? Curr Opin HIV AIDS. 2010 Nov;5(6):463-6. doi: 10.1097/COH.0b013e32833ed177. PMID: 20978388; PMCID: PMC3078627.
World Parkinson’s Congress 2023 recording How can we track pd using blood- and tissue-based biomarkers?
