Abstract
BACKGROUND: Rare diseases often entail significant challenges in clinical management and health-related quality of life (HRQoL) assessment. HRQoL assessment tools for rare diseases show substantial variability in outcomes, influenced by disease heterogeneity, intervention types, and scale characteristics. The variability in reported quality of life (QoL) improvements following interventions reflects a need to evaluate the effectiveness of HRQoL assessment tools and understand their suitability across diverse contexts. OBJECTIVE: This systematic review aims to analyse the effectiveness of various assessment scales in evaluating QoL and explores the general trends observed in the studies using the same and different assessment scales on rare diseases. METHODS: A comprehensive literature search was conducted across various databases to identify studies that reported QoL outcomes related to interventions for rare diseases. Search terms included various synonyms, and both the generic and specific terms related to rare diseases and QoL. Key variables, including intervention types, patient demographics, study design, and geographical factors, were analysed to determine their role in influencing the reported HRQoL outcomes. The findings were then compared with existing literature to identify consistent patterns and discrepancies. RESULTS: A total of 39 studies were included, comprising randomised controlled trials, observational studies, and cohort studies, with 4737 participants. Significant variations were observed in QoL improvements across studies, even when using the same assessment scales. These differences were primarily attributed to the heterogeneity in disease severity, intervention types, and patient characteristics. Studies employing disease-specific scales reported more nuanced outcomes than generic ones. Additionally, methodological differences, including study design and intervention type, contributed to variations in results and geographical factors influencing patients' perceptions of health and well-being. CONCLUSION: The reported differences in QoL outcomes across studies can be explained by a combination of factors, including disease heterogeneity, treatment modalities, patient demographics, and assessment scale characteristics. These findings underscore the importance of selecting appropriate HRQoL assessment tools based on the research context and patient population. For more accurate comparisons across studies, it is crucial to consider these factors alongside consistent methodology and cultural adaptability of scales. Future research should focus on developing standardised guidelines for QoL assessments that accommodate the diverse needs of patients with rare diseases.