Content validity and readability of patient-reported questionnaire instruments of hearing disability

Objective: This study evaluates the content validity (i.e. domains assessed) and readability levels of patient-reported questionnaire instruments using internationally recognised procedures and tools. Design: A review of the literature to identify candidate instruments and a synthesis of information including mapping extracted items onto the World Health Organisation's - International Classification of Functioning, Disability, and Health (WHO-ICF) and estimating readability. Study sample: 14 patient-reported questionnaire instruments. Results: In general, item content focussed on body function and on activity limitations and participation restrictions, with less emphasis on environmental and personal factors and with different emphases across instruments. Many items did not clearly map onto any of the WHO-ICF categories (i.e. not coded items ranged from 3.7 to 39.1% across the 14 questionnaires). All 14 instruments exceeded the sixth-grade reading level when calculated according to the FORCAST formula which is appropriate for assessing a non-narrative text. Conclusions: Clinical assessment of hearing disability is only as comprehensive as the items covered by the chosen measurement instrument. Our findings confirmed the diversity of domains covered by hearing disability instruments and gaps in assessment. Some concern is raised about whether the item content is appropriate for those respondents with poor literacy.