Objective: To evaluate diagnostic accuracy of dopamine SPECT against neuropathological diagnosis in a large cohort of patients with parkinsonism.

Background: Diagnosis of parkinsonian syndromes remains clinical with overall clinical diagnostic accuracy is 80%. Parkinson’s disease (PD), progressive supranuclear palsy (PSP) and multiple system atrophy (MSA) are characterised by striatal dopaminergic deficits and dopamine SPECT may be useful in their differential diagnosis. Despite its generalised use in clinical practice, dopamine SPECT diagnostic properties have never been assessed against the gold standard (neuropathological) diagnosis.

Method: All cases with dopamine SPECT as part of the clinical assessment of parkinsonism from the archive of the Queen Square Brain Bank were included. Cases presenting with pure dementia or ataxia syndromes were excluded. Dopamine SPECTs were documented as normal or abnormal based on reports from attending nuclear medicine physicians. Neuropathological diagnosis was made following consensus criteria. Diagnostic accuracy was compared between those with a pathological diagnosis of conditions known to have striatonigral dopaminergic deficits (PD, MSA and PSP) with a group of other parkinsonism.

Results: 112 cases with PD (n=13), PSP (n=65) or MSA (n=34) and a group of 19 cases of parkinsonism (8 corticobasal degeneration (CBD), 6 frontotemporal lobar degeneration (FTLD), 2 Alzheimer’s disease and 3 without identified proteinopathy) were included. 5 PSP (7.7%) and 3 MSA (8.8%) had a normal dopamine SPECT. In the other parkinsonism group, 9 cases (47.4%) had an abnormal dopamine SPECT (6 CBD, 3 FTLD). Compared to neuropathological diagnosis, dopamine SPECT had 92.9% sensitivity (95%CI: 86.4-96.9), 47.4% specificity (24.4-71.1), 91.2% positive predictive value (84.5-95.7) and 52.9% negative predictive value (27.8-77.0).

Conclusion: Neuropathological validation of the diagnostic properties of dopamine SPECT in patients with parkinsonism showed excellent sensitivity but limited specificity in our cohort. This was partly due to the abnormal SPECT results in conditions such as CBD and FTLD, although SPECT can also be normal in a minority of patients with PSP and MSA. These findings have important implications in clinical practice and clinical trials.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/diagnostic-accuracy-of-dopamine-spect-in-degenerative-parkinsonism-compared-to-neuropathological-diagnosis/