Monitoring Plasma Indicators in Parkinson’s Disease: A Longitudinal Study of Clusterin, Glutamic Acid Decarboxylase Antibodies, and Anti-Cyclic Citrullinated Peptide Antibodies

Objectives The investigation quantified plasma levels of three candidate biomarkers, clusterin (CLU), anti-cyclic citrullinated peptide (anti-CCP) antibodies, and anti-glutamic acid decarboxylase (anti-GAD) antibodies, in a cohort of patients with Parkinson’s disease (PD). The study further assessed longitudinal alterations of these markers in the context of pharmacological intervention, evaluating their discriminatory power against age-matched healthy controls. Material and Methods The study comprised 133 patients with PD and 142 healthy volunteers. Venous blood specimens were procured and processed according to standard immunological protocols, with biomarker quantification performed by enzyme-linked immunosorbent assay (ELISA). Statistically, the Wilcoxon signed ranks and the Mann-Whitney U test were employed for group comparisons, while diagnostic classification was refined by receiver operating characteristic curve analysis. Results Plasma concentrations of CLU and anti-CCP antibodies were markedly elevated in treatment-naive patients with PD relative to healthy controls ( p <0.0001 for both) and were significantly reduced after 60 days of treatment (CLU: mean change from 126.30 to 115.50 µg/mL; anti-CCP: mean change from 34.80 to 28.70 EU/mL) ( p <0.0001 for both), indicating their sensitivity to therapeutic intervention. No post-treatment change in anti-GAD antibody levels was observed, nor was the baseline difference between patients and controls statistically significant ( p >0.05). Receiver operating characteristic curve analysis yielded area under the curve values of 0.829 for CLU and 0.713 for anti-CCP, reflecting robust diagnostic discrimination. In contrast, anti-GAD achieved an area of 0.509, indicating a lack of diagnostic capability. Conclusion CLU and anti-CCP antibodies emerge as valuable plasma biomarkers for PD, with their significant post-treatment declines supporting their utility in both diagnosis and monitoring of therapeutic response, in distinction to anti-GAD antibodies, which show no similar link. The adoption of non-invasive plasma-based biomarkers has the potential to refine clinical evaluation and facilitate personalised care in PD. To substantiate these observations and clarify the biomarkers’ relevance to broader clinical practice, further studies with multicentre coordination, large sample sizes, and longitudinal design are imperative.