Patient involvement in rare disease trial design: Small populations making a big difference

Rare diseases are diseases with prevalence of lower than one in 2,000 individuals. Jointly, rare diseases affect many people in the world. Research in rare diseases is more challenging than in diseases that are more prevalent, due to small numbers, heterogeneity and often limited knowledge about the disease course and the pathophysiology underlying the disease.
This thesis has focused on two aspects of clinical research in rare diseases. In part one, patient involvement in rare disease research is investigated. Together with a group of rare disease patient representatives, we have developed a tool in which patient representatives together with researchers decide which outcome measures are relevant to patients, and can be added in a clinical trial.
In part two, we have investigated a measurement instrument: Goal Attainment Scaling (GAS). GAS is an assessment instrument that is intended for individual evaluation of an intervention. It allows patients to set individual goals, together with their treating professional. The number of goals and the content of these goals may differ per patient, but the attainment of the goals is measured in a standardized way. This makes a standardized evaluation of an intervention possible, even when the patients are all in a different stage of their disease. This can be an advantage in rare disease research, where the population is often small and heterogeneous. We conclude that more research on the validation of GAS is needed, and propose how GAS can be used and validated in the setting of rare disease trials.