Diagnostic accuracy of 18F-FP-CIT PET for clinically uncertain Parkinsonian syndrome

F-18-FP-CIT is a high-resolution imaging marker of nigrostriatal neuronal integrity, differentiating Parkinsonism with loss of dopaminergic terminals (presynaptic Parkinsonian syndrome [PS]) from Parkinsonism without nigrostriatal degeneration (non-PS). We assessed the diagnostic accuracy of F-18-FP-CIT PET in patients with clinically uncertain PS (CUPS) at the first visit. Among the 272 patients who underwent F-18-FP-CIT PET imaging at the first visit between September 2008 and July 2012, 111 had CUPS (age, 62.6 +/- 10.5 y; male:female, 45:66; symptom duration, 13.1 +/- 8.8 months). Uncertainty criteria included only one of the three cardinal signs of Parkinsonism, two signs without bradykinesia, or atypical signs. The baseline clinical and F-18-FP-CIT PET imaging diagnostic accuracy was compared with the accuracy of clinical diagnosis after > 2-year follow-up. Nuclear medicine physicians assessed the F-18-FP-CIT PET images visually. Focal dopamine transporter binding deficit in the posterior putamen was considered PS. Bilateral symmetric striatum without focal deficit, suggesting normal F-18-FP-CIT PET, and focal deficits elsewhere in the striatum suggesting vascular Parkinsonism were considered non-PS. Seventy-nine patients had PS, and 32 did not. Baseline clinical diagnosis included PS in 45 patients, non-PS in 24, and inconclusive in 42. Among patients in whom initial clinical diagnosis (PS or non-PS) was possible, the sensitivity, specificity, and accuracy of the baseline clinical and F-18-FP-CIT PET imaging diagnoses were 54.4, 50.0, and 53.2%, and 98.7, 100, and 99.1%, respectively. The respective positive and negative predictive values were 95.6 and 66.7%, and 100 and 97.0%. Among those with initially inconclusive diagnosis, 64.2% were eventually diagnosed with PS while 35.7% were diagnosed with non-PS. The final clinical diagnosis of these patients all matched those made by F-18-FP-CIT PET imaging, except in one patient with scan without evidence of dopaminergic deficit (SWEDD). F-18-FP-CIT PET diagnosis was more accurate than clinical diagnosis, reducing the false-negative and inconclusive clinical diagnosis rates at baseline in patients with CUPS.

Automated summary

This study aims to evaluate the diagnostic accuracy of F-18-FP-CIT PET in patients with clinically uncertain Parkinsonism. The results show that compared to baseline clinical diagnosis, F-18-FP-CIT PET is more accurate in diagnosing CUPS, reducing the false-negative and inconclusive diagnosis rates at baseline.