158 Chapter 8 Development and Validation of a domain- specific PROM in otology The development of the Otology Questionnaire Amsterdam (OQUA) covering all relevant ear complaints is presented in this thesis. This ear-domain specific questionnaire can be particularly useful as many patients with an ear complaint report multiple ear complaints simultaneously. The OQUA addresses, in a 34-item questionnaire, the eight most common types of ear complaints (earache, pressure sensation, itching, tinnitus, hearing loss, ear discharge, loss of taste and dizziness) each as a separate subscale and it contains one subscale about impact (of these ear complaints). The OQUA is developed based on thorough analyses including in-depth interviews and think-aloud interviews with patients, pilot studies and extensive field-testing. The OQUA was purposely designed as an ear-domain specific otology questionnaire to cover a wide range of ear complaints, rather than being limited to a specific ear condition (disease specific) or one single complaint (complaint specific) (see chapter 1, Figure 1). In the design of the OQUA, a formative model was used to calculate separate scores for each ear complaint scale. This contrasts with many other PROMs that combine responses into a single total score, which could neutralize certain negative and positive results to a normal score. The OQUA captures the different complaints distinctly, including the effects of these complaints on quality of life, without masking contrasting changes in other specific complaints. For example, if an individual’s hearing ability has improved due to a successful intervention, but dizziness has increased, many questionnaires will not notice this negative development (e.g. SPOT-25) or this development will not have a huge effect on the total score (e.g.COMQ12).1,2 Of course, one could argue that these questionnaires are measuring what they aim to measure, so the design can be considered flawless and good, but the outcome is then very specific. Thus, a major strength of the OQUA is the use of clearly separated complaints and an impact scale. Some multiple ear complaint PROMs, like COQOL and COMQ-12, do include quality of life questions but calculate only a total score.1,3 Other questionnaires have subscale scores, but illogical with random minimum and maximum scores, often calculated as a sum of the various scores or need to be combined with a generic questionnaire for quality of life.4,5 Reflecting on our OQUA validation study (chapter 4), we can conclude that the OQUA shows satisfactory results for construct validity, (test-retest) reliability and
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