Page 161 - Demo

Development and validation of the TSC-PROM1596Strengths, limitations and future directionsThe TSC-PROM provides an innovative tool to measure what is relevant to individuals with TSC, taking into account the complexity and heterogeneity of the clinical picture of TSC. It has been developed together with individuals with TSC and according to the gold standard COSMIN, providing high relevancy and good quality. It might serve as an example for future work for heterogeneous and complex disorders where existing instruments are unavailable for proxy-report and the domains of interest.However, limitations of this study are the sample size and representation of a limited number of countries and languages, as there will be differences between countries and cultures regarding healthcare systems. According to COSMIN criteria, a sample size between 50 and 100 per age group is regarded a good sample size for establishing internal consistency and reliability in a PROM.34 We aimed for a representative sample size of 200 participants, but a part of the participants did not complete the questionnaire battery. The majority of participants were from the Netherlands, although Belgium, American, Canadian, British, Spanish, and Finnish nationalities were included as well, as we recruited in the Netherlands, Belgium, and the United States without restrictions on nationality. In this study, we started to develop a Dutch and English instrument which was tested in the three participating countries. We have not yet examined the applicability for other countries, neither whether cultural adaptations are needed. Next, the TSCPROM should be translated into other languages such that all individuals with TSC could benefit regardless of their language, country or culture, ensuring inclusivity. Future interventional studies should evaluate responsiveness to change, test-retest validity and cross-cultural validity of the TSC-PROM and elaborate on discrepancies in functioning between self-reports and proxy-reports in which both the self and proxy versions are completed for one individual. Also, a shortened version of the TSC-PROM or more advanced psychometric methods such as item response theory (IRT-)based instruments might be developed for individuals with mild ID.77 Ideally, a generic measure should be developed applicable to all rare genetic neurodevelopmental disorders with appropriate versions for different levels of ID with different symptom Annelieke Muller sHL.indd 159 14-11-2023 09:07