Parkinson’s often correctly diagnosed, but challenges remain
Study finds examination of brain tissue after death remains a 'gold standard'
Despite an accuracy rate of 91% in diagnosing Parkinson’s disease, misdiagnoses still occur in the clinic, particularly with Lewy body dementia being mistaken for Parkinson’s — the two share some symptoms — or people with Parkinson’s being incorrectly told they have Alzheimer’s disease, researchers report.
“The findings of this study underscore the persistent challenges in achieving an accurate in-vivo diagnosis of [Parkinson’s] using clinical criteria alone,” they wrote in “Validating the Accuracy of Parkinson’s Disease Clinical Diagnosis: A UK Brain Bank Case–Control Study,” which was published in the Annals of Neurology.
Determining that a person has Parkinson’s, they added, “still suffers from a not satisfying accuracy, with the post-mortem examination as the gold standard for diagnosis.”
Parkinson’s often confirmed after other possible diseases are ruled out
Diagnosing Parkinson’s can be difficult and time consuming due to the absence of a definitive single test. Physicians typically rely on a combination of observed disease-related symptoms and the exclusion of other diseases with overlapping features. This process often involves multiple assessments and consultations, with a confirmed diagnosis usually established only after other possible diseases have been ruled out.
Despite ongoing efforts to refine diagnostic criteria and better understand the disease’s underlying mechanisms, accurately diagnosing Parkinson’s in living patients (in vivo) remains a challenge.
Researchers in Italy drew on medical records from the U.K. Brain Bank — a collection of tissue samples donated by people with and without diagnosed diseases upon their death — to determine how well clinical diagnoses of Parkinson’s during a person’s lifetime match with post-mortem findings.
Data examined covered 1,048 individuals diagnosed with Parkinson’s and 1,242 others without a clinical diagnosis in life of Parkinson’s or any disease.
Of the 1,048 Parkinson’s patients, 852 were confirmed to have the disease in post-mortem brain tissue (true positives), while 196 were not (false positives). Among the 1,242 people with no diagnosed disease, brain tissue examination showed 11 had Parkinson’s (false negatives), while the remaining 1,231 correctly did not (true negatives).
This led to a sensitivity of 99% and specificity of 86%, meaning that 99% of Parkinson’s patients were correctly identified while alive (sensitivity), while 14% were mistakenly diagnosed as having the disease (specificity). Diagnostic accuracy, or the potential to correctly identify the presence or absence of Parkinson’s, was 91%.
Among people with false positives for Parkinson’s, Lewy body dementia was the common correct diagnosis (19.4%) based on post-mortem brain tissue. Dementia with Lewy bodies is characterized by motor symptoms similar to those of Parkinson’s, but with earlier changes in cognition. It is caused, like Parkinson’s, by abnormal deposits of the alpha-synuclein protein in the brain.
‘Significant diagnostic error’ seen in post-mortem brain tissue examination
To find out how many diagnoses of Parkinson’s were missed, the researchers drew on data from 993 other people with a post-mortem Parkinson’s diagnosis — one based on changes observed in their brain tissue — and 1,288 individuals without apparent post-mortem tissue changes.
Among the 993 patients, 842 were correctly diagnosed during life (true positives), while 151 with the disease went undiagnosed (false negatives). Among the 1,288 with no apparent disease, five had been misdiagnosed with Parkinson’s (false positives), while 1,283 correctly were identified as having no known pathology (true negatives).
This resulted in a sensitivity of 84.8% and a specificity of 99.6%, with a diagnostic accuracy of 93.2%. Among clinically misdiagnosed patients, 28 (18.5%) were diagnosed with Alzheimer’s, while a nearly equal number either were given no disease diagnosis (17.8%) or were diagnosed with another neurodegenerative disease.
Despite advancements in diagnostic criteria and guidelines, the researchers considered the accuracy and specificity of Parkinson’s diagnosis during a patient’s lifetime inadequate. “Identifying more solid in-vivo biomarkers, improving the characterization of prodromal [early] symptoms and risk factors, and increasing knowledge of [disease-causing processes] are required steps to augment the diagnostic process,” they wrote.
“Our findings confirm a still significant diagnostic error and emphasize the need for more fine and homogeneous criteria to classify idiopathic [of unknown cause] Parkinson’s patients correctly,” the team concluded.
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