Development and Validation of an Iranian Voice Quality of Life Profile (IVQLP) Based on a Classic and Rasch Rating Scale Model (RSM)

Abstract

No culture based instrument exists for the people of Iran to measure outcomes of voice disorders. The objective of this study was to develop a statistically and culturally robust tool for assessing voice disorder outcomes in the Iranian population. A 65-item assessment tool called the Iranian Voice Quality of Life Profile (IVQLP) was developed after three stages of study. IVQLP measures voice disorder outcomes in four domains: physical, emotional, functional, and cultural. The questionnaire was given to 130 individuals with various voice disorders and 30 control subjects with no vocal pathology. The data obtained were subjected to measures of reliability (internal consistency and test-retest) and validity (content, construct, and concurrent) in the classic sense, as well as examined based on Rasch rating scale model analysis. Results showed that IVQLP had high internal consistency (α = 0.99) and test-retest reliability (r = 0/90). IVQLP differentiated the dysphonic group from the control group. Findings using the classic models suggested adequate construct validity for 43 items of the IVQLP fit the Rasch model. The high Rasch item separation reliability, separation index, and strata statistics for 43 items indicated that IVQLP provided further evidence that the items are reliable and comprehensive representations of quality of life concepts in Iranian people with voice disorders. This study concludes that IVQLP is a sufficiently reliable and valid tool to measure Iranian patients' perception of their quality of life in respect to their voice problem.