Experts have questioned attempts to cluster cases of Parkinson’s disease into subtypes.
The subtypes currently used "have questionable applicability and relevance", say Dr Tiago Mestre of the Ottawa Hospital, Canada, and colleagues.
Writing in IOS Press recently, the group explain that Parkinson’s disease is known for its heterogeneity in symptoms and underlying biology. "One approach is to identify subtypes of patients with a set of differentiating features at a clinical, biological, genetic or pathological level," they write.
An international Task Force for Parkinson’s Disease Subtypes was convened in 2018.
The new work reviews 38 studies on the quality and clinical applicability of various subtyping systems.
Most often, motor characteristics were used to differentiate subtypes. In terms of clinical applicability, the value of differentiating between subtypes was low.
"Subtyping studies undertaken to date have significant methodologic shortcomings and most have questionable clinical applicability and unknown biological relevance," the team report.
"The clinical and biological signature of Parkinson’s disease may be unique to the individual, rendering Parkinson’s disease resistant to meaningful cluster solutions."
Dr Mestre said: “Having reviewed the existing literature on subtyping and explored the methodologic pitfalls and challenges associated with performing the optimal subtyping studies described above, it is time to re-evaluate our approach to understanding and describing Parkinson’s disease heterogeneity.
“We have provided recommendations and formulated questions that, once addressed, will inform new approaches to better explain the variability in Parkinson’s disease including emphasis on the variability at an individual level, more aligned with future application of personalised medicine principles.”
Mestre, T. A. et al. Parkinson’s Disease Subtypes: Critical Appraisal and Recommendations. IOS Press 13 April 2021 doi: 10.3233/JPD-202472
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