ABSTRACT
BACKGROUND: Fabry disease is a rare X-linked lysosomal storage disorder. It is associated with physical distress and social challenges that may affect adults differently compared to pediatric patients. However, there is no disease-specific quality of life (QOL) scale that can provide a detailed assessment of QOL for adults with Fabry disease. Therefore, we aimed to determine the factor structure and assess the validity of a scale that was created to assess the QOL of adult patients with Fabry disease. This study was conducted in two phases. First, scale feasibility was confirmed through a questionnaire survey of nine patients. Second, a cross-sectional questionnaire survey of patients (aged ≥ 18 years) diagnosed with Fabry disease was conducted. Item development and refinement were conducted based on guidelines for scale development. Exploratory factor analysis was used to clarify the factor structure and confirm internal consistency. As a measure of QOL, construct validity was of the scale was verified based on its correlations with the Short Form-8 (SF-8) scale. RESULTS: The newly created Adult Fabry Disease QOL (AFQOL) scale comprises 39 items that cover five factors: "neuropathic pain and abdominal symptoms," "impact on work and school," "relationship challenges," "ophthalmologic and otolaryngologic symptoms," and "cardiovascular and renal symptoms." Cronbach's alpha coefficient for all factors was above 0.8, and the AFQOL total scores were significantly correlated with the physical and mental components of the SF-8 (rs = - 0.508 and - 0.400, respectively). CONCLUSIONS: The AFQOL scale assesses physical symptoms and social difficulties experienced by adult patients with Fabry disease. A strength of the scale is its ability to assess the impact of work and relationships on patients. The scale can be useful in objectively assessing QOL for a group or for individual patients. Future research should explore further aspects of the scale's validity and reliability.
Adults with Fabry disease experience severe challenges, which adversely impact their quality of life (QOL). As it is a rare disease, non-patients lack awareness of the severity of its symptoms and the resultant social difficulties of the patients. Most instruments that measure QOL are not specific enough to address issues related to Fabry disease. Therefore, in this study, a measurement instrument known as the Adult Fabry QOL (AFQOL) scale was designed and validated. The 39-item scale covers five domains that are congruent with the symptoms of adult Fabry disease. It differs from other QOL scales as it also assesses the impact of work and personal relationships on patients' QOL and symptoms that progress in adulthood. This study has important implications for healthcare providers who treat adult patients with Fabry disease, enabling them to have a fuller picture of the unique needs of this population.
ABSTRACT
Introduction: Fabry disease is a rare, X-linked lysosomal storage disorder that begins in childhood with a wide variety of symptoms, including neuropathic pain, gastrointestinal abnormalities, and skin abnormalities. Despite the substantial impact of these symptoms on children's quality of life (QOL), systematic QOL analysis of Japanese pediatric Fabry disease patients has been limited. Therefore, to evaluate the QOL of Japanese pediatric Fabry disease patients using standardized and disease-specific scales, we used the Fabry-specific Pediatric Health and Pain Questionnaire (FPHPQ), which was developed by the Fabry Outcome Survey. Methods: The FPHPQ was translated in accordance with the Principles of Good Practice for the Translation and Cultural Adaptation Process for Patient-Reported Outcomes. A back-translated version was reviewed twice by the original lead author of FPHPQ to confirm the conceptual equivalence. The questionnaire was then validated by cognitive debriefing, and distributed to pediatric Fabry disease patients in Japan. Results: Questionnaire responses were obtained from eight patients. The mean scores on the FPHPQ were 11.0 (± 11.43) for heat-associated pain, 5.5 (± 4.60) for cold-associated pain, and 14.8 (± 5.97) for abdominal pain and fatigue. In addition, heat-associated pain negatively correlated with physical well-being, whereas cold-associated pain positively correlated with good friendships. Conclusion: We established the Japanese version of the FPHPQ to assess the QOL of pediatric Fabry disease patients. The internal consistency and partial criterion-related validity of the Japanese version were confirmed. Analysis of a larger number of patients should be performed in the future to further validate the outcomes of this study.
ABSTRACT
INTRODUCTION: Lysosomal storage disorders and peroxisomal disorders are rare diseases caused by the accumulation of substrates of the metabolic pathway within lysosomes and peroxisomes, respectively. Owing to the rarity of these diseases, the prevalence of lysosomal storage disorders and peroxisomal disorders in Japan is unknown. Therefore, we conducted a nationwide survey to estimate the number of patients with lysosomal storage disorders and peroxisomal disorders in Japan. METHODS: A nationwide survey was conducted following the "Manual of nationwide epidemiological survey for understanding patient number and clinical epidemiology of rare diseases (3rd version)". A questionnaire asking for detailed information, such as disease phenotypes and medical history, was created and sent to 504 institutions with doctors who have experience in treating patients with lysosomal storage disorders and peroxisomal disorders. Result A total of 303 completed questionnaires were collected from 504 institutions (response rate: 60.1%). The number of patients was estimated by calculating the rate/frequency of overlap. The estimated number of patients was 1658 (±264.8) for Fabry disease, 72 (±11.3) for mucopolysaccharidosis I, 275 (±49.9) for mucopolysaccharidosis II, 211 (±31.3) for Gaucher disease, 124 (±25.8) for Pompe disease, 83 (±44.3) for metachromatic leukodystrophy, 57 (±9.4) for Niemann-Pick type C, and 262 (±42.3) for adrenoleukodystrophy. In addition the birth prevalence was calculated using the estimated number of patients and birth year data for each disease, and was 1.25 for Fabry disease, 0.09 for mucopolysaccharidosis I, 0.38 for mucopolysaccharidosis II, 0.19 for Gaucher disease, 0.14 for Pompe disease, 0.16 for metachromatic leukodystrophy, 0.16 for Niemann-Pick type C, and 0.20 for adrenoleukodystrophy. DISCUSSION: Among the diseases analyzed, the disease with the highest prevalence was Fabry disease, followed by mucopolysaccharidosis II, adrenoleukodystrophy, Gaucher disease and metachromatic leukodystrophy. In particular, the high prevalence of mucopolysaccharidosis II and Gaucher disease type II was a feature characteristic of Japan. CONCLUSION: We estimated the number of patients with lysosomal storage disorders and peroxisomal disorders in Japan. The details of the age at diagnosis and treatment methods for each disease were clarified, and will be useful for the early diagnosis of these patients and to provide appropriate treatments. Furthermore, our results suggest that supportive care and the development of an environment that can provide optimal medical care is important in the future.
