title: Reproducibility and diagnostic accuracy of substantia nigra sonography for the diagnosis of Parkinson's disease.
abstract: OBJECTIVE
  Transcranial sonography (TCS) shows characteristic hyperechogenicity of the substantia nigra (SN) in patients with Parkinson's disease (PD). Although this feature is well established, sufficient observer reliability and diagnostic accuracy are prerequisites for advancements of this method.
  
  
  METHODS
  The authors investigated both aspects in a cross-sectional study with four blinded TCS raters in 22 PD patients and 10 healthy controls.
  
  
  RESULTS
  As expected, the authors found significant bilateral SN hyperechogenicity in PD patients. Quantitative computerised SN planimetry had a substantial intra- (intraclass correlation coefficient (ICC) 0.97 and 0.93 respectively for both hemispheres) and inter-rater reliability (ICC 0.84 and 0.89), while visual semiquantitative echogenicity grading of the SN revealed a moderate intrarater (weighted kappa 0.80 ipsilateral and 0.74 contralateral) and slight (0.33) to fair (0.51) inter-rater reliability only. Diagnostic accuracy measured as the area under the curve of receiver-operating characteristics plots was highest in TCS of the SN opposite the clinically most affected body side (planimetry 0.821, echogenicity grading 0.792) with a hyperechogenic area of 0.24 cm(2) as the optimum cut-off value for the differentiation between PD and controls (sensitivity 79%, specificity 81%).
  
  
  CONCLUSIONS
  The data demonstrate that the observer variability of SN planimetry is low in the hands of experienced investigators. This approach also offers adequate diagnostic accuracy. The authors conclude that reliable SN TCS data on PD can be achieved in clinical routine and multicentre trials when standardised analysis protocols and certain quality criteria of brain parenchyma sonography are met.
authors.affiliation: Department of Neurology, University Hospital, Goethe-University, Frankfurt am Main, Germany.
authors.forename: Simone
authors.initials: S
authors.lastname: van de Loo
authors.forename: Uwe
authors.initials: U
authors.lastname: Walter
authors.forename: Stefanie
authors.initials: S
authors.lastname: Behnke
authors.forename: Johann
authors.initials: J
authors.lastname: Hagenah
authors.forename: Matthias
authors.initials: M
authors.lastname: Lorenz
authors.forename: Matthias
authors.initials: M
authors.lastname: Sitzer
authors.forename: Rüdiger
authors.initials: R
authors.lastname: Hilker
authors.forename: Daniela
authors.initials: D
authors.lastname: Berg
mesh_terms: D000368:Aged; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000473:pathology; D011237:Predictive Value of Tests; D012372:ROC Curve; D015203:Reproducibility of Results; D013378:Substantia Nigra / Q000000981:diagnostic imaging* / Q000473:pathology; D017585:Ultrasonography, Doppler, Transcranial / Q000379:methods*