Genomic Testing in Australia: A Budget Impact Analysis Using Diffusion Modelling from a Healthcare System Perspective.

Background: Genomic testing can shorten the diagnostic odyssey for people with rare diseases, yet clinical uptake has lagged funding policy in Australia. We evaluated the 10-year budget impact of alternative implementation strategies for publicly funded genomic testing using national claims data and diffusion modelling.

Methods: Monthly Medicare Benefits Schedule (MBS) claims (1993-2025) were analyzed for chromosomal microarray analysis (CMA), Fragile X (FMR1) testing, and genomic tests across seven rare-disease groups (syndromic and non-syndromic intellectual disability, neuromuscular, inherited cardiac, renal ciliopathies/tubulopathies, congenital hearing loss, mitochondrial). Logistic, Gompertz, and Bass diffusion functions and SARIMA were fitted to uptake and used to forecast 2025-2034 volumes. Scenarios included: status quo; broadened second-line eligibility; and first-line ES/GS replacing CMA/FMR1 (60:40 ES:GS). Costs used 1 July 2024 MBS schedule fees; results are in AUD.

Results: Observed genomic testing volumes were below diffusion-implied trajectories. Ten-year cumulative spending was: status quo AUD 1.1m; broadened second-line AUD 7.5m (incremental +6.4m vs status quo); and first-line ES/GS AUD 6.2m (incremental +5.1m). In 2028, status quo AUD 0.23m, second-line AUD 1.21m, first-line AUD 0.97m. ES/GS achieved lower cumulative spend than broadened second-line despite higher per-test fees, reflecting substitution from CMA/FMR1 and efficient diagnostic pathways.

Conclusions: Indication-by-indication funding has yielded slower-than-expected uptake and likely under-budgeting. A first-line genomic testing pathway, aligned with CMA criteria, could better match clinical need while constraining spend vs expanding second-line eligibility. Harmonized eligibility and streamlined implementation would improve access and planning.