Norwegian version of the Edinburgh cognitive and behavioural ALS screen: Construct validity, internal consistency, inter-rater, and test-retest reliability.

Background: Research collaboration highlight a need for validated tests in other languages than English. Translation and culture adjustments may threaten essential features of the original instrument.

Objective: To assess the internal consistency, inter-rater and test-retest reliability, and construct validity of the Norwegian version of the Edinburgh Cognitive and Behavioural Amyotrophic Lateral Sclerosis (ALS) Screen (ECAS-N).

Methods: Performance of 71 subjects with ALS, 85 healthy controls (HC) and 6 controls with Alzheimer's disease (AD) were assessed with the ECAS-N. Test-retest interval was four months. Internal consistency was evaluated using Cronbach's alpha; reliability was assessed using intraclass correlation coefficient (ICC), Cohen's kappa, and Bland Altman plot. Five hypothesis, including the Montreal Cognitive Assessment (MoCA) screen, was evaluated for construct validity.

Results: ECAS-N total score produced a Cronbach's alpha of 0.65, had excellent inter-rater reliability (ICC = 0.99) and acceptable test-retest reliability (ICC = 0.73). Construct validity analysis suggested valid use of the ECAS-N to distinguish people with ALS-specific cognitive impairment from HC (p = 0.001) and those with AD (p = 0.002). The MoCA and ECAS-N were moderately correlated (r = 0.53).

Conclusion: The ECAS-N has potential to be used by different testers in clinical practice and research to screen patients with ALS who speak Norwegian and for documenting cognitive impairment over time.