Expanded EP-QuIC Testing for Sporadic CJD in a Local Geographic Area of Canada Results in Improved Surveillance

BACKGROUND: Diagnosis of sporadic Creutzfeldt-Jakob disease (sCJD) has traditionally relied on non-specific cerebrospinal fluid (CSF) biomarkers such as 14-3-3γ and total tau. The development of quaking-induced conversion (QuIC) assays has enabled direct detection of prion seeds, improving antemortem diagnostic accuracy. We previously noted a high CSF submission rate from the Canadian province of New Brunswick. We leveraged this observation to evaluate how expanded regional testing influences prion disease surveillance and the diagnostic performance of EP-QuIC. METHODS: CSF submissions between 2016 and 2024 from all provinces to the Public Health Agency of Canada's National Microbiology Laboratory were considered, and EP-QuIC results were analyzed in the context of biomarker profiles and patient demographics. Biochemical subtype distribution was examined to assess whether increased testing density facilitates the detection of subtypes with less common clinical presentations. RESULTS: The CSF submissions provided an opportunity to assess EP-QuIC performance in a cohort with increased testing rates. EP-QuIC maintained high diagnostic reliability, demonstrating strong performance even when clinical suspicion was expected to be low. Additionally, a modest rise in VV2 cases was observed, suggesting that broader testing could improve the identification of those sCJD subtypes that may not initially meet criteria for classic CJD and could otherwise be underrecognized. CONCLUSION: Enhanced regional EP-QuIC testing supports more robust prion disease surveillance and retains high diagnostic accuracy across varied clinical contexts. Increased testing density may also improve detection of some sCJD subtypes, highlighting the value of increased access to EP-QuIC testing.