title: Reliability and validity of an instrument for the assessment of bradykinesia.
abstract: Bradykinesia is associated with reduced quality of life and medication non-compliance, and it may be a prodrome for schizophrenia. Therefore, screening/monitoring for subtle bradykinesia is of clinical and scientific importance. This study investigated the validity and reliability of such an instrument. Included were 70 patients with psychotic disorders. Inertial sensors captured mean cycle duration, amplitude and velocity of four movement tasks: walking, elbow flexion/extension, forearm pronation/supination and leg agility. The concurrent validity with the Unified Parkinson's Disease Rating Scale (UPDRS) bradykinesia subscale was determined using regression analysis. Reliability was investigated with the intra-class correlation coefficient. The duration, amplitude and velocities of the four tasks measured by the instrument explained 67% of the variance on the UPDRS bradykinesia subscale. The instrument test-retest reliability was high. The instrument investigated in this study is a valid and reliable alternative to observer-rated scales. It is an ideal tool for monitoring bradykinesia as it requires little training and experience to achieve reliable results.
authors.affiliation: Psychiatric Centre GGz Centraal, Innova, Amersfoort, The Netherlands; Department of Psychiatry and Psychology, Maastricht University, Maastricht, The Netherlands. Electronic address: t.mentzel@ggzcentraal.nl.
authors.forename: Thierry Q
authors.initials: TQ
authors.lastname: Mentzel
authors.affiliation: Department of Psychiatry and Psychology, Maastricht University, Maastricht, The Netherlands. Electronic address: r.lieverse@maastrichtuniversity.nl.
authors.forename: Ritsaert
authors.initials: R
authors.lastname: Lieverse
authors.affiliation: Department of Psychiatry, University Medical Centre Utrecht, Utrecht University, Utrecht, The Netherlands. Electronic address: amarlevens@hotmail.com.
authors.forename: Amar
authors.initials: A
authors.lastname: Levens
authors.affiliation: Psychiatric Centre GGz Centraal, Innova, Amersfoort, The Netherlands; Department of Psychiatry and Psychology, Maastricht University, Maastricht, The Netherlands. Electronic address: c.mentzel@ggzcentraal.nl.
authors.forename: Charlotte L
authors.initials: CL
authors.lastname: Mentzel
authors.affiliation: Psychiatric Centre GGz Centraal, Innova, Amersfoort, The Netherlands; Department of Psychiatry, University Medical Centre Utrecht, Utrecht University, Utrecht, The Netherlands. Electronic address: d.tenback@ggzcentraal.nl.
authors.forename: Diederik E
authors.initials: DE
authors.lastname: Tenback
authors.affiliation: Psychiatric Centre GGz Centraal, Innova, Amersfoort, The Netherlands; Department of Psychiatry and Psychology, Maastricht University, Maastricht, The Netherlands. Electronic address: r.doornebal-bakker@ggzcentraal.nl.
authors.forename: P Rob
authors.initials: PR
authors.lastname: Bakker
authors.affiliation: MOVE Research Institute, Faculty of Human Movement Sciences, VU University, Amsterdam, The Netherlands; Nederlandse Organisatie voor Toegepast Natuurwetenschappelijk Onderzoek (TNO) [Dutch Organization for Applied Scientific Research], Soesterberg, The Netherlands. Electronic address: hein.daanen@tno.nl.
authors.forename: Hein A M
authors.initials: HAM
authors.lastname: Daanen
authors.affiliation: Psychiatric Centre GGz Centraal, Innova, Amersfoort, The Netherlands; Department of Psychiatry and Psychology, Maastricht University, Maastricht, The Netherlands. Electronic address: p.vanharten@ggzcentraal.nl.
authors.forename: Peter N
authors.initials: PN
authors.lastname: van Harten
mesh_terms: D000328:Adult; D000368:Aged; D004550:Elbow / Q000503:physiopathology; D005080:Exercise Test / Q000379:methods*; D005260:Female; D005542:Forearm / Q000503:physiopathology; D006801:Humans; D018476:Hypokinesia / Q000175:diagnosis*; D007866:Leg / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D011618:Psychotic Disorders / Q000503:physiopathology*; D012044:Regression Analysis; D015203:Reproducibility of Results; D016138:Walking
keywords: Antipsychotic-induced; Diagnostic techniques and procedures; Extrapyramidal disorders; Micro-electrical-mechanical systems; Parkinsonism; Reproducibility of findings; Schizophrenia and disorders with psychotic features