Baseline [123I]FP-CIT SPECT (DaTSCAN) severity correlates with medication use at 3 years in Parkinson's disease

Background Presynaptic dopaminergicdeficiency on dopamine transporterimaging supports a clinical diagnosis of Parkinson's disease and correlates with the severity of rigidity and bradykinesia. Baseline dopaminergicdeficiency predicts clinical severity, but the relationship with subsequent medication use has not been reported. Methods A randomly selected cross section of 83 Parkinson's disease (PD) patients who had [123I] FP-CIT SPECT at the time of clinical diagnosis was identified. Dopaminergicdeficiency was graded 1, 2 or 3 with increasing severity using visual assessment and by semiquantitative analysis of putamen and caudate uptake. Antiparkinson medicationusage and clinical severity by Hoehn and Yahr were noted annually to 3 years. Results In 83 patients (66% male, median age 65.0 years, IQ 55.4–71.8), [123I]FP-CIT SPECT was grade 1 in 20 (24%), grade 2 in 53 (64%) and grade 3 in 10 patients (12%). Dopamine transporteruptake ratios were inversely associated with antiparkinson medicationusage (r = −0.26, P = 0.0201) and Hoehn Yahr stage (r = −0.32, P = 0.0029) at 3 years from baseline, but there was considerable variation in drug usage in individual patients. At 3 years, patients with grade 1 scans at baseline received a median dose of 325 levodopaequivalent units (LEU) ( interquartile range175–433); grade 2 scan patients 400 LEU ( interquartile range300–635); and grade 3 scan patients 460 LEU ( interquartile range252–658). Conclusion The degree of reduction in presynaptic dopaminergicuptake at baseline is associated with higher antiparkinson drugdosage at follow-up, but the wide variation means that the baseline FP-CIT SPECT does not reliably predict drug use in individual cases.