DOES CLINICAL INTOLERANCE TO A DIAGNOSTIC ACUTE LEVODOPA CHALLENGE DIFFERENTIATE MULTIPLE SYSTEM ATROPHY FROM PD?

Background: The diagnosis of multiple system atrophy (MSA) remains challenging. Objective: To determine if the occurrence of symptoms of clinical intolerance such as nausea, vomiting, hypotension, and profuse perspiration during a standard acute levodopa challenge may be a useful marker of MSA. Methods: A total of 507 dopaminergic acute challenge tests performed for different purposes in the last 10 years in a movement disorders clinic were reviewed, identifying patients who manifested symptoms of clinical intolerance during test performance. Only those tests completed for diagnostic purposes were included and these were matched by the presence or absence of response to levodopa, sex, and age, with a group of patients undergoing acute challenge without any symptoms of clinical intolerance. Presumptive diagnosis for each patient was performed by means of accepted clinical criteria after a significant follow-up period. Only patients with a final diagnosis of Parkinson's disease (PD) or MSA were analyzed. Results: Twenty-three out of the 507 patients (women: 50%) presented symptoms of clinical intolerance and received a final diagnosis of PD or MSA, and underwent further analysis. Four out the 23 patients with intolerance (17%) and one out the 16 patients from the control group (6%) were diagnosed as having MSA (Chi-square = 1.05, p = .3). Overall sensitivity and specificity of the presence of clinical intolerance to predict diagnosis of MSA were 80% (95% IC: 45%-100%) and 44% (95% CI: 27%-61%) respectively. Conclusions: Symptoms of clinical intolerance during an acute levodopa challenge do not appear to be useful in the diagnosis of MSA.