Diagnostic Value of 123I-Ioflupane and 123I-Iodobenzamide SPECT Scans in 248 Patients with Parkinsonian Syndromes

Background: SPECT is one of the most employed techniques in the diagnostic workup of idiopathic Parkinson’s disease (IPD). Despite its widespread use, the exact diagnostic accuracy of this technique in parkinsonian syndromes remains controversial. Methods: In this study, we investigated the diagnostic accuracy of an initial 123 I-ioflupane (FP-CIT) and/or 123 I-iodobenzamide (IBZM) SPECT to differentiate between IPD and other parkinsonian disorders. 248 patients underwent a SPECT scan because of an as yet unclassified parkinsonian syndrome in our clinic between 2001 and 2006. Gold standard was the clinical diagnosis derived from the latest available clinical record, or, when this was not possible, a new complete physical and neurological examination by a blinded movement disorder specialist neurologist. Mean follow-up between SPECT and the latest clinical information was 18 months (range 3 months to 5 years). Results: 223 of the 248 patients were clinically definitely diagnosed after follow-up: IPD 127, atypical parkinsonian syndromes (APS) 27, essential tremor (ET) 22, vascular parkinsonism (VP) 16, drug-induced parkinsonism (DIP) 5, doubt between PD and APS 2, other diseases without dopaminergic involvement 24. The mean odds ratio (95% CI) for FP-CIT SPECT’s ability to distinguish between IPD and ET was 82 (11–674); between IPD and VP 61 (8–490); between IPD and DIP 36 (2–697) and between IPD and APS was 1 (0–4). The odds ratio for the IBZM SPECT tracer to differentiate between IPD and APS was 7 (2–17). Conclusions: FP-CIT SPECT is accurate to differentiate patients with IPD from those with ET, and IPD from VP and DIP. The accuracy of both FP-CIT and IBZM SPECT scans to differentiate between IPD and APS is low.