Earlier differential diagnosis of parkinsonism possible

Researchers have developed an image-based classification algorithm that has high specificity in distinguishing between parkinsonian disorders and could help in selecting treatment for early stage patients and identifying participants for clinical trials. Writing in Lancet Neurology the researchers used fluorine-18-labelled-fluorodeoxyglucose-PET to differentiate between idiopathic Parkinson’s disease, multiple system atrophy, and progressive supranuclear palsy in 167 patients with parkinsonism with unclear underlying disease. They then used an automated voxel based classification procedure to calculate each patient’s likelihood of having each of the three diseases. After imaging, patients were assessed by movement disorders specialists (who were blinded to the PET results) for over 2 years before a final clinical diagnosis was made. The accuracy of the initial image-based classification was assessed by comparison with the final clinical diagnosis. The researchers found that image-based classification for idiopathic Parkinson’s disease had 84% sensitivity, 97% specificity, 98% positive predictive value (PPV), and 82% negative predictive value (NPV). Imaging classifications were also accurate for multiple system atrophy (85% sensitivity, 96% specificity, 97% PPV, and 83% NPV) and progressive supranuclear palsy (88% sensitivity, 94% specificity, 91% PPV, and 92% NPV). The researchers say that while their classification approach cannot be used to differentiate other forms of parkinsonism, once specific patterns for these other forms are identified and validated they can be included in the algorithm. While the availability of easy-to-apply diagnostic procedures such as metabolic and dopamine transporter imaging is encouraging, the results are no replacement for thorough clinical investigation, Dr Angelo Antonni (Venice and Parkinson Institute, Milan) said in an accompanying editorial. “Patients should be referred to movement disorder neurologists, particularly in cases of uncertainty,” he said, adding that he expected these procedures to find their natural place in the identification of suitable candidates for drug trials of complex surgical procedures. Lancet Neurology 2010; published online before print...