Mayo RT-QuIC Prion CSF (RTQPC) and CJD Evaluation profile (CJDE)

Mayo Clinic Laboratories in Rochester, Minnesota offers a second-generation CSF RT-QuIC prion assay as test RTQPC, which cannot be ordered alone but only inside two CSF profiles: CJDE, the Creutzfeldt-Jakob Disease Evaluation, and RPDE, the Rapidly Progressive Dementia Evaluation. CJDE pairs the prion assay with total tau, phospho-tau and their ratio for patients where prion disease is strongly suspected; RPDE adds an Alzheimer disease marker panel for patients where Alzheimer disease is also plausible. It is a laboratory developed test, not cleared or approved by the FDA. It is the second US laboratory service for CSF RT-QuIC alongside the NPDPSC, and the NPDPSC surveillance page counts 156 Mayo-tested positives in its probable cases for 2024 to mid 2026. Information only, not medical advice.

Key facts

  • RTQPC uses the method Real-Time Quaking-Induced Conversion on CSF and is orderable only as part of the CJDE or RPDE profile.
  • CJDE has three parts: the RT-QuIC prion assay, a tau CJD evaluation (total tau, phospho-tau and ratio) and a written medical interpretation; reference values are negative RT-QuIC, total tau at or below 393 pg/mL and t-tau/p-tau at or below 18.
  • CJDE is intended when prion disease is strongly suspected on clinical or MRI grounds; RPDE is the suggested route when Alzheimer disease seems likelier.
  • Specimen: two unaliquoted CSF tubes of 1.5 to 2.5 mL each, first 1 to 2 mL discarded, frozen preferred; stability is 28 days frozen, 14 days refrigerated and 12 hours at ambient temperature.
  • RPDE requires polypropylene tubes because polystyrene can falsely lower Abeta42.
  • RTQPC is run on Monday, Tuesday, Thursday and Sunday in Rochester with reports usually available in 3 to 8 days.
  • Regulatory status: developed and validated by Mayo under CLIA, not FDA cleared or approved; CPT 0584U and result LOINC 101662-5.
  • Per search excerpts of the catalog (page itself blocked), Mayo states that second-generation CSF RT-QuIC has been consistently reported at sensitivity of at least 92 percent and specificity of at least 99 percent; this is framed as literature experience, not clearly as Mayo's own validation.
  • The same excerpts say false negatives occur mainly in genetic prion disease (fatal familial insomnia and GSS are named) and in atypical sporadic subtypes such as MM2 cortical, that small amounts of blood in CSF can cause false negatives, and that repeat testing may be considered when suspicion stays high.
  • Mayo marketing material claims specificity above 99 percent for ruling out non-prion causes of rapidly progressive dementia and positions the profile as available only through Mayo; seen as excerpt only.
  • For comparison, the NPDPSC quotes RT-QuIC sensitivity 90.3 percent and specificity 98.5 percent from a 2020 Neurology study, an analytic time of 5 business days after receipt, no STAT service, and rejects bloody or colored CSF.
  • The NPDPSC reports that its probable-case counts include positive RT-QuIC results tested at Mayo: 12 of 406 probable cases in 2024, 88 of 390 in 2025 and 56 of 203 in 2026 to 30 June, 156 in all.

Timeline

  1. 2015NPDPSC introduces second-generation CSF RT-QuIC in the US (per a search excerpt of its page, not opened separately).
  2. 2024First 12 Mayo-tested RT-QuIC positives appear in NPDPSC probable-case counts.
  3. 202588 Mayo-tested positives counted by NPDPSC.
  4. 2025Mayo Insights post on the new test for separating prion disease from other causes of rapid dementia (date taken from the page address; page blocked).
  5. 2026NPDPSC surveillance data updated, showing 56 Mayo-tested positives for 2026 to date.

Last checked 1 November 2026

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