TABLE 3.

Utility of testing by type of prion disease suspected

Disease(s)	Most helpful premortem testing	Least helpful premortem testing
sCJD (∼90% of prion disease)	DWI, MRI, and RT-QuIC have high sensitivity and specificity; MRI accuracy is best when interpreted by somebody with extensive expertise in prion MRI	EEG is often not abnormal until late in disease, if at all; 14-3-3 sensitivity and specificity are poor
gCJD (∼10% of prion disease)	PRNP gene sequencing is diagnostic; MRI and RT-QuIC have high overall sensitivity and specificity, but accuracy may depend on specific mutation	EEG is often not abnormal until late in disease, if at all; 14-3-3 sensitivity and specificity are poor
FFI, GSS (<5% of prion disease)	PRNP gene sequencing is diagnostic in the setting of the appropriate clinical syndrome	CSF laboratory tests (RT-QuIC, 14-3-3, tau), EEG, and MRI are often within normal limits
vCJD (rare form of prion disease)	FLAIR MRI with characteristic pulvinar sign	EEG, 14-3-3, and RT-QuIC are frequently negative in vCJD