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Updated: Oct 7, 2026
Prion Safety Laboratory Swipe Test
Published on: February 14, 2025
Potential misclassification of probable sporadic Creutzfeldt-Jakob disease diagnosed without PRNP testing
Koki Kosami1, Tsuyoshi Hamaguchi2, Hitaru Kishida3
1Division of Public Health, Center for Community Medicine, Jichi Medical University, Tochigi 329-0498, Japan.
Background:
Although probable sporadic Creutzfeldt-Jakob Disease (CJD) can be diagnosed without prion protein gene (PRNP) testing, some patients with genetic prion disease may meet the diagnostic criteria for sporadic CJD. We aimed to assess the potential for such misclassification in the absence of genetic information.
Methods:
We analyzed data from the nationwide prospective registry of prion diseases in Japan. For patients diagnosed with probable sporadic CJD, clinical characteristics were compared according to whether PRNP testing had been performed. In addition, patients with genetic prion diseases were reclassified to evaluate potential misclassification as sporadic CJD.
Results:
A total of 3008 patients with sporadic CJD and 1143 with genetic prion diseases were analyzed. Tested and Not-Tested groups differed in age at onset (difference, -1 year; 95% CI, -3 to -1) and CSF RT-QuIC positivity (difference, 8.2%; 95% CI, 3.4 to 13.2). The median survival time was 11.9 months for the Tested group and 9.8 months for the Not-Tested group. The proportions of misclassification after reclassification of patients with genetic prion diseases (95% CI) were 82.9% (75.5, 88.5) for E200K, 24.1% (20.9, 27.6) for V180I, 72.7% (64.6, 79.6) for M232R, 12.3% (8.1, 18.2) for P102L, 0% (0, 13.8) for P105L, and 10% (1.8, 40.4) for D178N.
Conclusions:
A substantial proportion of patients with genetic prion disease may meet the clinical diagnostic criteria for sporadic CJD. Opportunities for PRNP testing may be limited in patients with rapidly progressive disease.
