Vernetti, Patricio Millar

Abstract Background The Movement Disorder Society (MDS) research criteria for possible prodromal multiple system atrophy (PP‐MSA) have not been prospectively validated. Objective To evaluate the diagnostic performance of the PP‐MSA criteria in a longitudinal cohort of patients with pure autonomic failure (PAF) and to assess whether additional clinical features improve their predictive value. Methods Seventy‐six patients with PAF enrolled across eight centers in the Natural History Study of the Synucleinopathies were followed for ≥6 years or until phenoconversion. Participants were classified according to MDS PP‐MSA criteria and followed for development of MSA, Parkinson's disease, or dementia with Lewy bodies. Diagnostic performance was assessed longitudinally. Analyses were repeated using a stricter olfactory threshold (University of Pennsylvania Smell Identification Test [UPSIT]≤28) as an exclusion criterion. Results Thirty‐eight participants met PP‐MSA criteria, of whom 12 phenoconverted to MSA within 6 years. Sensitivity was 100% at year 1 and 92% at year 6, whereas specificity ranged from 56% to 67%. Positive predictive value (PPV) ranged from 21% to 34%. Applying a stricter olfactory threshold improved specificity (90%–97%) and PPV (53%–83%), with a modest reduction in sensitivity (to 83%). Participants who phenoconverted to MSA were younger, had more severe urinary dysfunction, and greater orthostatic heart rate responses. Conclusions The PP‐MSA criteria demonstrate high sensitivity but limited specificity in patients with PAF. A stricter olfactory threshold improves diagnostic performance and may enhance cohort enrichment for clinical trials. © 2026 International Parkinson and Movement Disorder Society. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

Abstract We aimed to describe the clinical features of patients with pure autonomic failure (PAF) preceding phenoconversion that could be useful as predictive markers for advancing α-synuclein-associated neurodegeneration of the brain. Patients diagnosed with PAF were evaluated at eight centres (seven US-based and one European) and enrolled in a longitudinal observational cohort study (NCT01799915). Subjects underwent detailed assessments of motor, sleep, olfactory, cognitive and autonomic function and were followed prospectively to determine whether they developed parkinsonism or dementia for up to 10 years. We identified incident cases of Parkinson's disease (PD), dementia with Lewy bodies (DLB) or multiple system atrophy (MSA) and computed hazard ratios for phenoconversion as functions of clinical features. A total of 209 participants with PAF with a median disease duration of 6 years (IQR: 3–10) were enrolled. Of those, 149 provided follow-up information at an office or telemedicine visit. After a mean follow-up duration of 3 years, 48 (33%) participants phenoconverted (42% to PD, 35% to DLB and 23% to MSA). Faster phenoconversion from study enrolment to any diagnosis was associated with urinary and sexual dysfunction [hazard ratio (HR) 5.9, 95% confidence interval (CI): 1.6–22 and HR: 3.6, 95% CI: 1.1–12] followed by subtle motor signs (HR: 2.7, 95% CI: 1.2–6), trouble swallowing (HR 2.5, 95% CI: 1.4–4.5) and changes in speech (HR:2.4, 95% CI:1.1–4.8) at enrolment. Subjects reporting deterioration of handwriting were more likely to phenoconvert to PD (HR: 2.6, 95% CI: 1.1–5.9) and those reporting difficulty handling utensils were more likely to phenoconvert to DLB (HR: 6.8, 95% CI: 1.2–38). Patients with a younger age of PAF onset (HR: 11, 95% CI: 2.6–46), preserved olfaction (HR: 8.7, 95% CI: 1.7–45), anhidrosis (HR: 1.8, 95% CI: 1–3.1, P = 0.042) and severe urinary problems (HR 1.6, 95% CI: 1–2.5, P = 0.033) were more likely to phenoconvert to MSA. The best autonomic predictor of PD was a blunted heart rate increase during the tilt-table test (HR: 6.1, 95% CI: 1.4–26). Patients with PAF have an estimated 12% (95% CI: 9–15%) per year annual risk following study entry of phenoconverting to a manifest CNS synucleinopathy.