14 Chapter 1 develop, for example after surgery or due to progression of the disease. When the patient has or develops multiple complaints, a complaint-specific questionnaire is inadequate or even falsely ‘proving’ success through a small focus. In general, it can be argued that the more specific a PROM is, the narrower its applicability (applicable to less patients, but more specific to a disease or complaint). And the less specific a PROM is, like the SF-36, the wider the applicability but the less specific the information on a certain disease or symptom (Figure 1). In otology, a domain-specific PROM could serve as a bridge between disease-specific and generic PROMs. It should cover ear-related complaints that are common across a wide range of ear diseases. If a variety of patients is seen in an ENT practice, using one ear-domain specific PROM could be a good solution, as using many different (disease- or complaint-specific) PROMs seems not very practical for the ENT surgeon. Practical steps for development of a PROM When starting this project there was no domain-specific questionnaire available, covering all ear complaints and the impact of these complaints. It was decided to develop the Otology Questionnaire Amsterdam (OQUA), and the developmental process is described in this thesis (chapter 3). A quality guideline, COSMIN, was used to develop the OQUA.15,16 According to the COSMIN guidelines, there are six to seven practical steps involved in the development of a questionnaire. Step one is to conduct a systematic literature review of the existing PROMs which is necessary to provide a comprehensive overview of the full spectrum of a particular symptom, disease or domain. This review can also result in the identification of an existing suitable PROM or inspire ideas for a new instrument. Using, translating, or adapting an existing PROM can save considerable time and effort. Additionally, the review can provide insights into how the PROM should be structured, offering guidance on what to include or avoid in its design. The second step is to define and elaborate the construct that one intends to measure. Then, the underlying relationship between the items and the construct to be measured (conceptual framework) needs to be established. This involves clearly identifying what you want to measure, in what population for what purpose, in what setting and ensuring that it is specific and well-understood. Next, in the third step, you need to decide on the measurement method. This step involves choosing the most suitable approach for measuring the construct. It could be a questionnaire, a rating scale or a physical test. The fourth step involves selecting and formulating the items. Experts play a crucial role in this process. Clinicians with extensive experience treating large
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