Purpose: To examine the diagnostic sensitivity and specificity of dopamine transporter SPECT imaging with a highly dopamine transporter selective radioligand. The study included consecutively enrolled, drug-naive patients with an average short history of parkinsonian motor symptoms, referred for diagnostic scanning.
Methods: The study group comprised 288 patients naive to antiparkinson treatment who were enrolled as they were admitted for a diagnostic SPECT scan with the radioligand [(123)I]-N-(3-iodoprop-2E-enyl)-2-β-carbomethoxy-3β-(4-methylphenyl)nortropane ((123)I-PE2I). After the diagnostic scanning, patients were followed clinically with an average follow-up of 19.7 ± 12.5 months.
Results: A diagnosis could be clinically settled in 189 patients and among these patients, a dopamine transporter scan had a sensitivity of 88% and a specificity of 91% for discrimination between patients with and without striatal neurodegeneration. In cognitively impaired patients (Mini Mental State Examination <27) the specificity was 75% and the sensitivity 95%. A striatal anterior-posterior ratio (APR) of >2 differentiated between idiopathic Parkinson's disease and atypical parkinsonian syndromes with a specificity of 84% and a sensitivity of 63%.
Conclusion: In drug-naive patients with subtle clinical parkinsonian motor symptoms, dopamine transporter scan using (123)I-PE21 has a high sensitivity and specificity in distinguishing between patients with and without striatal neurodegeneration. The specificity is lower in patients who are also cognitively impaired. Calculation of the striatal APR can assist in differentiating between idiopathic Parkinson's disease and atypical parkinsonian syndromes.