Rare neurodegenerative diseases monitored in Spain: the situation in the Valencian Region

Abstract Background Rare neurodegenerative diseases (RND) are progressive conditions that damage nerve cells, often including movement disorders, cognitive decline, and loss of motor function. Aim to characterize people with RND and describe their capture in the Rare Diseases population-based registry of Valencian Region (SIER-CV). Methods Cross-sectional study, using SIER-CV to identify the RND prevalent cases between 2010-2022 including: Niemann-Pick type C (NPC), Amyotrophic Lateral Sclerosis (ALS), Huntington Disease (HD) and Friederich Ataxia (FA). Sources of capture were: Hospital Discharge Database (CMBD), CMBD of Major Ambulatory Surgery (CMBDCMA) and Mortality Registry (MR). The distribution of cases by RND, sex and capture source, and mean age at capture, diagnosis and death were calculated. Total and by RND prevalence were obtained, and for cases captured automatically, positive predictive value (PPV) by RND was calculated. Results 2111 cases of RND were identified: 5 NPC, 1543 ALS, 475 HD and 88 FA. The 51.3% were men. Mean age of capture was 64 years, at diagnosis 60.4 years (available in 66.7% of cases) and at death 70.8 years. A total of 78.3% died, ALS was the RND with most of the deaths (87.8%). In 2022, RND prevalence was 86 cases per million inhabitants, and HD was the most prevalent (42 cases/million). 96 cases were captured by active search and 2015 cases by automated capture sources: 88.3% from CMBD, 81.9% from MR and 1.3% from CMBDCMA. The PPV by RND was: 3.3% for NPC, 40.7% for AF, 80.4% for ALS and 80.8% for HD. Conclusions Most RND cases correspond to ALS, which is also the one that presented the most deaths and therefore was not the most prevalent. These findings would be useful for health planning and for the differential approach to RND. VPP variability shows automated capture cannot be addressed in the same way for all RND. As these RND are part of the National Rare Disease Registry, the results of this study may be replicated in other Spanish regions. Key messages • Automated data capture is useful for rare disease population-based registries and rare diseases surveillance but manual reviews remain needed for some diseases. • Differences in predictive value indicates that the procedures and approaches should be done by disease but could be done equally across Spain.