title: Diagnostic accuracy of apparent diffusion coefficient and 123I-metaiodobenzylguanidine for differentiation of multiple system atrophy and Parkinson's disease.
abstract: BACKGROUND
  It is often hard to differentiate Parkinson's disease (PD) and parkinsonian variant of multiple system atrophy (MSA-P), especially in the early stages. Cardiac sympathetic denervation and putaminal rarefaction are specific findings for PD and MSA-P, respectively.
  
  
  OBJECTIVE
  We investigated diagnostic accuracy of putaminal apparent diffusion coefficient (ADC) test for MSA-P and (123)I-metaiodobenzylguanidine (MIBG) scintigram for PD, especially in early-stage patients.
  
  
  METHODS
  The referral standard diagnosis of PD and MSA-P were the diagnostic criteria of the United Kingdom Parkinson's Disease Society Brain Bank Criteria and the second consensus criteria, respectively. Based on the referral standard criteria, diagnostic accuracy [area under the receiver-operator characteristic curve (AUC), sensitivity and specificity] of the ADC and MIBG tests was estimated retrospectively. Diagnostic accuracy of these tests performed within 3 years of symptom onset was also investigated.
  
  
  RESULTS
  ADC and MIBG tests were performed on 138 patients (20 MSA and 118 PD). AUC was 0.95 and 0.83 for the ADC and MIBG tests, respectively. Sensitivity and specificity were 85.0% and 89.0% for MSA-P diagnosis by ADC test and 67.0% and 80.0% for PD diagnosis by MIBG test. When these tests were restricted to patients with disease duration ≤ 3 years, the sensitivity and specificity were 75.0% and 91.4% for the ADC test (MSA-P diagnosis) and 47.7% and 92.3% for the MIBG test (PD diagnosis).
  
  
  CONCLUSIONS
  Both tests were useful in differentiating between PD and MSA-P, even in the early stages. In early-stage patients, elevated putaminal ADC was a diagnostic marker for MSA-P. Despite high specificity of the MIBG test, careful neurological history and examinations were required for PD diagnosis because of possible false-negative results.
authors.affiliation: Clinical Research Center, National Hospital of Utano, Kyoto, Japan. murray@ecohealthalliance.org
authors.forename: Atsushi
authors.initials: A
authors.lastname: Umemura
authors.forename: Tomoko
authors.initials: T
authors.lastname: Oeda
authors.forename: Ryutaro
authors.initials: R
authors.lastname: Hayashi
authors.forename: Satoshi
authors.initials: S
authors.lastname: Tomita
authors.forename: Masayuki
authors.initials: M
authors.lastname: Kohsaka
authors.forename: Kenji
authors.initials: K
authors.lastname: Yamamoto
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Sawada
mesh_terms: D019797:3-Iodobenzylguanidine; D000368:Aged; D003937:Diagnosis, Differential; D004058:Diffusion; D005260:Female; D006801:Humans; D008297:Male; D019578:Multiple System Atrophy / Q000000981:diagnostic imaging*; D010300:Parkinson Disease / Q000000981:diagnostic imaging*; D011699:Putamen / Q000000981:diagnostic imaging; D011877:Radionuclide Imaging
chemical_list: D019797:3-Iodobenzylguanidine