Reliability and validity of an instrument for the assessment of bradykinesia

Thierry Q. Mentzel*, Ritsaert Lieverse, Amar Levens, Charlotte L. Mentzel, Diederik E. Tenback, P. Rob Bakker, Hein A. M. Daanen, Peter van Harten

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

18 Citations (Web of Science)


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.
Original languageEnglish
Pages (from-to)189-195
JournalPsychiatry Research
Publication statusPublished - 30 Apr 2016


  • Parkinsonism
  • Extrapyramidal disorders
  • Antipsychotic-induced
  • Diagnostic techniques and procedures
  • Schizophrenia and disorders with psychotic features
  • Reproducibility of findings
  • Micro-electrical-mechanical systems

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