Objectives: Niemann-Pick disease type C (NPC) is a rare life-limiting disease for which there is no cure. No scales currently exist to measure the impact of medication, physical therapy or clinical trials. The aim of this study was to develop age-appropriate Quality-of-Life (QoL) scales to measure the impact of NPC on children and adults.
Design: Scale development study using a phenomenological approach to data generation and analysis.
Methods: Fourteen interviews were conducted with people living with NPC and/or their parents/carers. Themes were generated and examined against an existential-phenomenological theory of wellbeing. A matrix was constructed to represent the phenomenological insight gained on participants' subjective experiences and a bank of items that were related to their QoL was developed.
Results: NPC quality-of-life questionnaires for children (NPCQLQ-C) and adults (NPCQLQ-A) proxy prototype scales were produced and completed by 23 parents/carers of children (child age mean = 8.61 years) and 20 parents/carers of adults (adult age = 33.4 years). Reliability analysis resulted in a 15-item NPCQLQ-C and a 30-item NPCQLQ-A, which showed excellent internal consistency, Cronbach's α = 0.925 and 0.947, respectively.
Conclusion: The NPCQLQ-C and NPCQLQ-A are the first disease-specific QoL scales to be developed for people living with NPC. This novel approach to scale development values the experiential, real life impact of living with NPC and focused on the lived-experiences and impact on QoL. The scales will enable healthcare professionals and researchers to have a better understanding and quantifiable measurement of the impact of living with NPC on a patient's daily life.
Keywords: Lifeworld theory; Niemann-Pick type C; Phenomenology; Proxy scales; Quality of life.