Evaluating Health-Related Quality of Life (HRQoL) scales for rare diseases from a Quality of Life (QoL) perspective

Although rare diseases concern a small fragment of the population, they collectively affect about 4% of the general population. The well-being of patients with rare diseases has long been overlooked, but several scales now measure their health-related quality of life (HRQoL), enabling targeted cures and interventions. However, not all scales are equally efficient at measuring key aspects of quality of life of patients. In the present study, we evaluate health related quality of life (HRQoL) scales for rare diseases from the perspective of the social science-driven field of quality of life (QOL). Using the method of Booysen to evaluate social indicators, we review eleven scales frequently used in the case of rare diseases (CFQ, CFQoL, DLQI, MOS, PLC, QLI, SF-12, SF-36, SIP, Skindex, TAAQOL) and map what is measured and what is not. Key findings are that scales are overly focused on output-based specific indicators, lack flexibility, and miss a holistic view of quality of life. We suggest improvements such as incorporating more generic items, including input indicators, targeting general well-being, and involving patients in the development of questions.