Parkinson’s misdiagnoses in Finland illustrate need for better criteria
About 1 in 8 patients were later given a different diagnosis
Nearly 1 in 8 people diagnosed with Parkinson’s disease in Finland within the past couple of decades were later given a different diagnosis, usually within two years, underscoring the need for better clinical criteria and regular checkups.
When Parkinson’s and dementia with Lewy bodies, a neurodegenerative disease also marked by a buildup of toxic clumps of misfolded alpha-synuclein protein, were treated as separate diagnoses, the rates of misdiagnoses increased further.
“Had the study been restricted to early-stage cases, the rate of diagnostic alterations would likely have been even higher. Therefore, despite recent advancements in clinical criteria and diagnostic technologies, variability in diagnoses continues to be a significant issue,” researchers wrote. Their study, “Stability and Accuracy of a Diagnosis of Parkinson Disease Over 10 Years,” was published in Neurology and led by Valtteri Kaasinen, MD, PhD, a professor of neurology at the University of Turku, Finland, and chief physician at the Neurocenter of Turku University Hospital.
“The key conclusions of our study are the urgent need for ongoing refinement of diagnostic processes, enhanced clinical training for neurologists, more frequent use of postmortem diagnostic confirmation, and the development of widely accessible, cost-effective biomarkers,” Kaasinen said in a university press release.
Diagnoses, misdiagnoses in Parkinson’s
Diagnosing Parkinson’s can be difficult, especially for doctors who aren’t specialists in movement disorders. While there have been advances in how Parkinson’s is diagnosed, misdiagnoses still occur. In their study, Kaasinen’s team evaluated the long-term consistency and accuracy of Parkinson’s diagnoses in 1,626 patients diagnosed with Parkinson’s between 2006 and 2020 at Turku University Hospital and three regional hospitals in both outpatient and inpatient settings. During this period, “Finland did not have an officially structured subspecialty in movement disorders, a situation shared by many other countries,” the researchers wrote.
Over a median follow-up of 10 years, 215 (13.3%) patients saw their diagnosis change. When Parkinson’s was treated as a separate diagnosis from dementia with Lewy bodies or monogenic Parkinson’s — that is, Parkinson’s caused by mutations in single genes — the number increased to 288 (17.7%). Dementia with Lewy bodies was diagnosed using the one-year rule, according to which dementia appears before or within a year of symptoms of Parkinson’s, along with problems with memory and visual hallucinations.
“This rule, which considers the temporal sequence of motor and cognitive symptoms, resulted in more latter cases identified compared to the original clinical diagnoses. While the one-year rule is used in clinical practice, its relevance may be limited by the overlap between these disorders, with substantial group-level differences, but minimal distinctions at the individual level,” Kaasinen said.
It took a median of nearly two years for a Parkinson’s diagnosis to be changed. The most common misdiagnoses were vascular parkinsonism, progressive supranuclear palsy, and multiple system atrophy. Some cases (4.7%) were classified as clinically undetermined parkinsonism.
“Notably, a majority of these diagnostic changes occur within the first two years of diagnosis, which emphasizes the challenges and uncertainty clinicians face in diagnosing Parkinson’s disease accurately,” Kaasinen said.
To help confirm their diagnoses, some patients underwent dopamine transporter imaging, which can detect reductions in dopamine activity in the brain and help distinguish parkinsonian disorders from other conditions. Dopamine is a chemical messenger involved in movement control whose levels gradually decline as nerve cells in the brain degenerate with the disease.
In a few cases, brain examinations were done after death and in nearly two-thirds (64%) of these cases, the initial Parkinson’s diagnosis was confirmed. Also, two movement disorder specialists reviewed patients’ records to see if the diagnoses remained accurate.
“This emphasizes the urgent need for ongoing refinement of diagnostic processes, enhanced clinical training for neurologists, more frequent use of postmortem diagnostic confirmation, and the development of widely accessible, cost-effective biomarkers,” the researchers wrote.
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