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 cm2 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.
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Competing interests SB was a grantee of the Michael J Fox Foundation. JH is funded by the Bachmann-Strauss Dystonia Parkinson Foundation and received honoraria as an invited speaker from GlaxoSmithKline. RH has received speaker honoraria from Medtronic, Orion, GlaxoSmithKline, TEVA, Cephalon, Solvay, Desitin and Boehringer Ingelheim as well as travel funding from Medtronic and Cephalon. He serves or has served on a scientific advisory board for Cephalon. He has received research funding from the Deutsche Parkinson Vereinigung (dPV) and the University of Frankfurt/Main. DB is principal investigator of multicentre trials funded by Novartis, Johnson and Johnson, Boehringer, Teva and Eisai. She is a member of advisory boards for Novartis, GlaxoSmithKline, Teva, Lundbeck and UCB, and has received speaker honoraria from UCB, GlaxoSmithKline, Teva, Lundbeck, Novartis and Merck Serono. Her work was funded by research grants from the Michael J Fox Foundation, BmBF, German Parkinson Asscociation and Tübingen University.
Ethics approval Ethics approval was provided by the Ethical committee of the medical faculty of Goethe University, Frankfurt am Main, Germany.
Provenance and peer review Not commissioned; externally peer reviewed
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