WHAT IS THE ACCURACY OF THE CLINICAL-DIAGNOSIS OF MULTIPLE SYSTEM ATROPHY - A CLINICOPATHOLOGICAL STUDY

Background: The presentation of symptoms for multiple system atrophy ( MSA) varies. Because there are no specific markers for its clinical di agnosis, the diagnosis rests on the results of the neuropathologic exa mination. Despite several clinicopathologic studies, the diagnostic ac curacy for MSA is unknown. Objectives: To determine the accuracy for t he clinical diagnosis of MSA and to identify, as early as possible, th ose features that would best predict MSA. Design: One hundred five aut opsy-confirmed cases of MSA and related disorders (MSA [n = 16], non-M SA [n = 89]) were presented as clinical vignettes to 6 neurologists (r aters) who were unaware of the study design. Raters identified the mai n clinical features and provided a diagnosis based on descriptions of the patients' first and last clinic visits. Methods: Interrater reliab ility was evaluated with the use of kappa statistics. Raters' diagnose s and those of the primary neurologists (who followed up the patients) were compared with the autopsy-confirmed diagnoses to estimate the se nsitivity and positive predictive values at the patients' first and la st visits. Logistic regression analysis was used to determine the best predictors to diagnose MSA. Results: For the first visit (median, 42 months after the onset of symptoms), the raters' sensitivity (median, 56%; range, 50%-69%) and positive predictive values (median, 76%; rang e, 61%-91%) for the clinical diagnosis of MSA were not optimal. For th e last visit (74 months after the onset of symptoms), the raters' sens itivity (median, 69%; range, 56%-94%) and positive predictive values ( median, 80%; range, 77%-92%) improved. Primary neurologists correctly identified 25% and 50% of the patients with MSA at the first and last visits, respectively. False-negative and -positive misdiagnoses freque ntly occurred in patients with Parkinson disease and progressive supra nuclear palsy. Early severe autonomic;failure, absence of cognitive im pairment, early cerebellar symptoms, and early gait disturbances were identified as the best predictive features to diagnose MSA. Conclusion s: The low sensitivity for the clinical diagnosis of MSA, particularly among neurologists who followed up these patients in the tertiary cen ters, suggests that this disorder is underdiagnosed. The misdiagnosis of MSA is usually due to its confusion with Parkinson disease or progr essive supranuclear palsy, thus compromising the research on all 3 dis orders.