OBJECTIVES: To translate the voice-related quality of life (V-RQOL) questionnaire into Danish and to test the validity and reliability of this Danish version of the V-RQOL instrument.
METHODS: The translation process was done using forward and backward translation followed by pretesting interviews, performed on 21 participants. The final Danish version was then tested for validity and reliability on 80 cases with voice disorders and 21 controls without voice disorders.
RESULTS: The Danish version proved to be valid and reliable. Validity was confirmed by convergent and discriminant validity, known-groups validity, clinical validity (Spearman correlation coefficient 0.64), confirmatory factor analysis, and Rasch analysis. The instrument showed no ceiling effects, but all items and the Social-Emotional domain showed substantial floor effects. The item-total correlations were all high (0.58-0.82) and none of the interitem correlations were low. Reliability was confirmed with regard to internal reliability (Cronbach's alpha 0.92) and test-retest reliability (interclass correlation coefficient 0.89).
CONCLUSION: Our study shows that the Danish translation of the V-RQOL questionnaire is a valid and reliable instrument suitable for the assessment of the dysphonic patient. The high floor effects, however, indicate that minor differences in voice problems between patients may not be captured in the lower end of the scale with regard to the individual item and the Social-Emotional domain.