title: Acute stepwise challenge test with levodopa in treated patients with parkinsonism.
abstract: OBJECTIVE
  The aim of this study was to establish a new stepwise type of acute challenge test with incremental doses of levodopa/benserazide, and verify its predictive value in follow-up diagnoses and outcomes of deep-brain stimulation (DBS) in treated patients with parkinsonism.
  
  
  METHODS
  Prospective cohort study.
  
  
  RESULTS
  The optimal cutoff points for UPDRS-III improvement in these stepwise levodopa tests. In this study, we established acute challenge tests with incremental doses of levodopa/benserazide (100/25mg, 150/37.5mg, 200/50mg and 300/75 mg) in treated patients with parkinsonism (n=175). The receiver operating characteristic (ROC) curves were plotted to compare peak UPDRS-III improvement of PD patients (n=112) with that of non-PD parkinsonism patients (n=63). The point on the ROC curve with the highest Youden index was defined as the optimal cutoff point in motor improvement for differential diagnoses. The results of the new tests were compared with follow-up diagnoses and the outcomes of DBS.
  
  
  RESULTS
  The optimal cutoff points for UPDRS-III improvement with maximal Youden Indices on ROC curves from the tests, with the four incremental doses of levodopa/benserazide, were 12.2% (100/25mg), 22.3% (150/37.5mg), 27.9% (200/50mg) and 33.4% (300/75 mg). The test showed significant correlation with follow-up diagnosis and the outcomes of DBS (P of Kappa <0.01).
  
  
  CONCLUSIONS
  The results suggested that the new acute stepwise levodopa challenge test is a useful tool for the diagnosis of PD.
authors.affiliation: Department of Neurology, Beijing Tiantan Hospital, Capital Medical University, Beijing, China. happyfym@gmail.com
authors.forename: Tao
authors.initials: T
authors.lastname: Feng
authors.forename: Wei
authors.initials: W
authors.lastname: Li
authors.forename: Linlong
authors.initials: L
authors.lastname: Lu
authors.forename: Yilong
authors.initials: Y
authors.lastname: Wang
authors.forename: Weixiong
authors.initials: W
authors.lastname: Shi
authors.forename: Jianguo
authors.initials: J
authors.lastname: Zhang
authors.forename: Yongjun
authors.initials: Y
authors.lastname: Wang
authors.forename: Piu
authors.initials: P
authors.lastname: Chan
mesh_terms: D017668:Age of Onset; D000368:Aged; D000978:Antiparkinson Agents / Q000008:administration & dosage / Q000627:therapeutic use; D001545:Benserazide / Q000627:therapeutic use; D015331:Cohort Studies; D046690:Deep Brain Stimulation / Q000379:methods*; D003710:Demography; D004305:Dose-Response Relationship, Drug; D004359:Drug Therapy, Combination; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007980:Levodopa / Q000008:administration & dosage / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D019578:Multiple System Atrophy / Q000628:therapy; D010300:Parkinson Disease / Q000188:drug therapy / Q000628:therapy*; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012372:ROC Curve; D016896:Treatment Outcome
chemical_list: D000978:Antiparkinson Agents; D007980:Levodopa; D001545:Benserazide