CSF RT-QuIC has very high specificity, so if this is positive in a progressive cognitive syndrome then a very confident clinical diagnosis of CJD can be made.
A formal surveillance classification of ‘definite CJD’ does require pathological confirmation, i.e. post-mortem examination of brain tissue for spongiform change and/or positive immunoreactivity to prion protein.
Discussing post mortem brain examination with family is encouraged, but family should not feel pressured to consent for this in typical cases supported by a positive CSF RT-QuIC, as diagnostic confidence is already very high (even though the surveillance definition will be ‘probable’ rather than ‘definite’).
Post-mortems in suspected cases of CJD are performed at the national referral sites for high-risk post-mortems in Christchurch or Auckland and samples may be sent overseas for further analysis. If this is planned, clinicians are encouraged to discuss post-mortems with family at an early stage, provide information sheets and consent forms in advance. The mortuary teams are aware of the need not to cause undue delay to funeral arrangements.
The Auckland LabPLUS website has useful resources, including information for clinicians, families and a post-mortem consent form.
For the South Island, please use the Canterbury information sheet and consent form: