The Radboud Dysarthria Assessment: Development and Clinimetric Evaluation

OBJECTIVE: In the absence of an adequate dysarthria assessment in the Netherlands, we developed the Radboud Dysarthria Assessment (RDA). This article describes its development and clinimetric evaluation. PATIENTS AND METHODS: Forty-three patients were assessed with the RDA. The recording forms were subjected to exploratory factor analysis and estimation of internal consistency. The self-evaluation questionnaire was tested for internal consistency and the severity scale for intra- and inter-rater reliability. Construct validity of the severity scale and questionnaire was determined by relating them to the Speech Handicap Index (SHI), Dutch sentence intelligibility assessment (NSVO-Z), and category fluency task. RESULTS: Exploratory factor analysis extracted 4 factors (articulation, resonance, phonation, respiration/prosody) yielding an explained variance of 70.3%. Each factor showed good internal consistency (Cronbach's α: 0.89-0.91). The self-evaluation questionnaire showed excellent internal consistency (Cronbach's α: 0.90). Intra-class correlation coefficients of the severity scale (0.85-0.86) showed good reliability. The severity scores and self-evaluation questionnaire correlated substantially to strongly with the SHI (rs = 0.40 and 0.80) and substantially with the NSVO-Z (rs = -0.65 and -0.52). CONCLUSIONS: The RDA is a valid and reliable tool, but further investigation is needed to demonstrate whether this instrument can successfully support speech-language therapists in correctly diagnosing the type of dysarthria.