Objective: To assess the role of DaTSCAN in the diagnosis of Parkinson disease (PD).
Methods: Using the sensitivity and specificity values obtained in the 2 studies that recently led the US Food and Drug Administration to approve the use of DaTSCAN for the diagnosis of PD, calculations were carried out to estimate the accuracy of the clinical diagnosis taking DaTSCAN findings as the standard of truth.
Results: In early PD, a clinical diagnosis of "possible" or "probable" PD has a sensitivity of 98% and a specificity of 67%. The specificity increases to 94% once the clinical diagnosis becomes established. The overall accuracy of the clinical diagnosis is 84% in early PD and 98% at later stages. The clinical diagnostic accuracy is mathematically identical to the diagnostic accuracy of DaTSCAN imaging.
Conclusions: In the absence of neuropathologic validation, the overall accuracy of a clinical diagnosis of PD is very high and mathematically identical to the accuracy of DaTSCAN imaging, which calls into question the use of radiotracer neuroimaging as a diagnostic tool in clinical practice.