Content validity, reliability, and agreement between in-person and video-call assessments of the modified bradykinesia rating scale (MBRS)

Purpose To investigate content validity, test-retest reliability, and inter-rater reliability, and agreement between in-person and video-call assessments of the Modified Bradykinesia Rating Scale (MBRS), a new instrument to assess different components of bradykinesia (speed, amplitude, and rhythm).Materials and Methods This methodological study followed the COSMIN guidelines. Content validity was evaluated by experienced health professionals using the Content Validity Index (CVI). For reliability analysis, two trained raters assessed individuals with PD using the MBRS and, 7 to 14 days later, rater 1 performed the second assessment in-person and a third assessment via video call. Intraclass Correlation Coefficient (ICC) was used (α = 5%).Results Nine professionals confirmed adequate content validity (CVI ≥ 0.80) for all items. Fifty-two individuals with PD (66.9 ± 6.2 years; 61.5% men) were included. The MBRS showed adequate measurement properties: test-retest reliability (ICC: 0.464 ≤ ICC≤ 0.745; p ≤ 0.001), inter-rater reliability (ICC: 0.266 ≤ ICC ≤ 0.537; p ≤ 0.003), and agreement between in-person and video-call assessments (ICC: 0.488≤ ICC≤ 0.741; p ≤ 0.001).Conclusions The MBRS demonstrated adequate content validity, test-retest, and inter-rater reliabilities and can be used in both in-person and video-call assessments.