Variable sensitivity and specificity reported in IPD due to different mutations, with performance better in IPD with a CJD phenotype (e.g., E200K) than slowly progressive IPD (e.g., P102L) (Cramm et al., 2015; Bongianni et al., 2017; Foutz et al., 2017; Franceschini et al., 2017; Lattanzio et al., 2017; Rhoads et al., 2020). One report of good diagnostic accuracy in slow IPD with RT-QuIC using recombinant human PrP substrate (Sano et al., 2013). The gene discussed is PRNP; the disease is Creutzfeldt Jacob disease.