Measuring the impact of rare diseases in Tasmania, Australia.

Abstract

Background: An ongoing challenge with rare diseases is limited data and, consequently, limited knowledge about the collective prevalence and impact of these conditions on individuals, families, and the health system, particularly in rural and regional areas. Using existing datasets, this project aimed to examine the epidemiology of and hospital activity for Tasmanians with rare diseases.

Methods: Rare diseases were defined as non-infectious diseases with a prevalence of less than 1 in 2000. An initial resource set of 1028 ICD-10-AM diagnostic codes was used to identify a cohort of Tasmanians with rare diseases in Tasmanian Health datasets (1 January 2007 until 31 December 2020). Validating the resource set using a small group with known rare diseases revealed limitations in ascertainment, and so an expanded set of 1940 ICD-10-AM diagnostic codes was developed by cross-referencing ICD-10-AM codes with Orphanet data. Cohort hospital activity and admission costs were compared to statewide data for the final year of the study, 01 January 2020 to 31 December 2020.

Results: Using the resource set of 1028 ICD-10-AM diagnostic codes, the period prevalence of rare diseases in Tasmania across all age groups was estimated at 3.5%, with a point prevalence of 1.5% in December 2020. In 2020, 3384 individuals within the Tasmanian rare disease cohort, representing 0.6% of the Tasmanian population, accessed the public hospital system and accounted for 5.6% of all admissions. The mean length of stay for rare disease-related hospital admissions was 5.0 days, compared to 3.3 days for non-rare disease-related admissions. The mean cost per admission for the rare disease cohort was AUD$11,310, compared to AUD$6475 for all admissions statewide. In 2020, using the expanded resource set, the total cost of public hospital admissions in Tasmania was estimated to be AUD$979 million, with rare disease-related hospital admissions accounting for 9.1% of this cost, increasing to 19.0% when the costs for all admissions for the rare disease patients were included.

Conclusions: Patients with rare diseases had more admissions, longer length of stay, and a higher average cost per admission. Patients with rare diseases have a disproportionate impact on statewide hospital activity and costs in Tasmania.