Abstract Background Recent studies identified increased cerebrospinal fluid (CSF) DOPA decarboxylase (DDC) as a promising biomarker for parkinsonian disorders, suggesting a compensation to dying dopaminergic neurons. A correlation with 123I‐FP‐CIT‐SPECT (DaT‐SPECT) imaging could shed light on this link. Objective The objective is to assess the relationship between CSF DDC levels and DaT‐SPECT binding values. Methods A total of 51 and 72 Parkinson's disease (PD) subjects with available DaT‐SPECT and CSF DDC levels were selected from the PPMI and Biopark cohorts, respectively. DDC levels were analyzed using proximity extension assay and correlated with DaT‐SPECT striatal binding ratios (SBR). All analyses were corrected for age and sex. Results CSF DDC levels in PD patients correlated negatively with DaT‐SPECT SBR in both putamen and caudate nucleus. Additionally, SBR decreased with increased DDC levels over time in PD patients. Conclusion CSF DDC levels negatively correlate with DaT‐SPECT SBR in levodopa‐treated PD. © 2024 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Increased CSF DOPA Decarboxylase Correlates with Lower DaT‐SPECT Binding: Analyses in Biopark and PPMI Cohorts