Diagnostic Value of Combined Acute Levodopa Challenge and Olfactory Testing to Predict Parkinson's Disease

Abstract

Background: The diagnosis of Parkinson's disease (PD) can be challenging early in the diseasecourse, when motor features are subtle. The objective of this study was to explore the diagnostic value ofcombining acute levodopa challenge and olfactory testing to predict PD.Methods: Data from 210 patients with a recent onset of parkinsonism who had at least 2 years of follow-upand underwent acute levodopa challenge for the clinical prediction of long-term dopaminergic response andhad olfactory testing with Sniffin? Sticks Test were evaluated. Single and combined diagnostic measures wereanalyzed.Results: After 2 years of follow-up, a PD diagnosis was confirmed in 157 patients who fulfilled United KingdomParkinson?s Disease Society Brain Bank criteria and was ruled out in 53. Sensitivity and specificity of acutelevodopa challenge to predict PD diagnosis were 0.71 and 0.94, respectively. Sensitivity and specificity ofolfactory tests were calculated according to the total olfactory score for hyposmia (0.61 and 0.77respectively), the hyposmia identification subscore (0.63 and 0.74, respectively), and the anosmia score (0.40and 0.85, respectively). The best combination identified was response to acute levodopa challenge togetherwith hyposmia according to the total olfactory score (sensitivity, 0.90; specificity, 0.74; positive predictivevalue, 0.91; negative predictive value, 0.72; accuracy, 0.86).Conclusion: The combination of response to acute levodopa challenge with hyposmia according to the totalolfactory score improved sensitivity for the early diagnosis of PD.