Reliability and validity of an instrument to measure quality of life in the dysarthric speaker

Objective: To develop a tool to measure quality of life (QOL) in the dysarthric speaker (QOL-DyS). Patients and Method: The study consisted of two phases: scale development and item reduction (phase 1), and reliability and validity analysis (phase 2). The 100-item 'Dysarthria from the Point of View of the Dysarthric Patient' questionnaire was used for item development; the data from 50 dysarthric patients were measured for internal consistency and the 40-item QOL-DyS was developed. A second group of 50 dysarthric patients and 30 control participants were recruited for phase 2. Internal consistency and test-retest reliability were analyzed through Cronbach's α coefficient and intraclass correlation coefficient (ICC), respectively. The scores obtained from the pathological and the control group were compared using the Mann-Whitney test. Finally, the correlation between the QOL-DyS and dysarthria severity was assessed using the Spearman test. Results: An excellent internal consistency (α = 0.90) and test-retest reliability (ICC = 0.98, 95% CI: 0.97-0.99) were found; the score difference between the dysarthric and control groups was significant (p <0.001). The QOL-DyS scores correlated positively with the severity of dysarthria (r = 0.43). Conclusion: The QOL-DyS is a reliable and valid tool to assess QOL in patients with dysarthria.