Cerebrospinal Fluid (CSF) EP-QuIC Test

End-Point Quaking-Induced Conversion (EP-QuIC) Test

Cerebrospinal fluid (CSF). Minimum volume of specimen required is 1.0 mL. Volumes less than 0.5 mL will be rejected as insufficient quantity (NSQ). To avoid false negative results, specimens must not exhibit hemolysis or visible blood, or appear discoloured or be xanthochromic.

Lumbar puncture: We recommend that the first 2 mL of CSF drawn by lumbar puncture not be submitted for EP-QuIC testing to avoid blood contamination.

Polypropylene, low binding tubes are recommended for storage of CSF. Freeze specimen as soon as possible after collection. Ship frozen on dry ice Monday to Wednesday to ensure receipt by Friday. Shipments of CSF specimens are not received on the weekend. Shipments must contain enough dry ice (>5kg) in a Styrofoam box inside a rigid outer package to withstand weather conditions and warehouse storage for up to four days.

Shipping of specimens shall be done by a TDG certified individual in accordance with TDG regulations. For additional information regarding classification of specimens for the purposes of shipping, consult either Part 2 Appendix 3 of the TDG Regulations or section 3.6.2 of the IATA Dangerous Goods Regulations as applicable.

Patients with a progressive neuropsychiatric syndrome that include CJD, GSS or FFI in the differential diagnosis.

Both pages of the Prion Diseases Section CSF EP-QuIC test requisition must be completed for the sample to be processed and reported. https://public.cnphi-rcrsp.ca/gts/main

Label the sample with the date of collection and a unique alphanumeric identifier, as these will be used for reporting to maintain patient confidentiality during fax transmission.

Testing is performed twice a week and results are sent by fax to the sending laboratory as listed on the requisition. Please include the appropriate fax number in the space provided on the requisition. Should a second centre/physician require a copy of the report, please include their contact information at the bottom of the requisition.

End-Point Quaking Induced Conversion (EP-QuIC) Test:

The NML offers the “end-point” quaking-induced conversion (EP-QuIC) test that has proven to be robust and reproducible, obviating the need to rely on the detection of non-specific markers of neurodegeneration (1).

The EP-QuIC test exploits the natural ability of the disease-associated, misfolded prion protein to act as a template for the conversion of the normal form. The CSF sample is added to wells containing in-house manufactured recombinant full-length prion protein as substrate. The mixture is heated to 42°C in a 96-well plate with vigorous, periodic shaking for 66 hours. Refolded recombinant prion protein forms amyloid fibrils that are detected by binding to the fluorescent dye, thioflavin T, which can be measured with a spectrofluorometer.

Samples are run in triplicate, and both positive and negative controls are run on each plate. A 4-fold relative increase in fluorescent signal over the 66-hour incubation for all three replicates is required for a positive test result. Occasionally, only one or two of the three replicates meet the threshold. In this case, the test is repeated using higher and lower concentrations of CSF. In most cases, a definitive test result is obtained following this step; however, if the test continues to produce inconsistent results across any dilution set, the EP-QuIC result is reported as indeterminate. On average, an indeterminate result occurs once every 100 samples. A negative result is reported when fluorescence in all three wells does not reach the threshold.

The sensitivity and specificity of the test are = 96% and = 99%, respectively (1,2).

A positive test result from EP-QuIC supports a probable diagnosis of a human prion disease in the clinical context of a progressive neuropsychiatric syndrome (3). This testing is for a provincially reportable and nationally notifiable disease and is therefore of public health concern. Please inform your appropriate provincial public health laboratory and provincial public health authorities of a positive test result.

14 calendar days from date of receipt at the National Microbiology Labs.

1. Slota JA, Myskiw J, Peterson A, et al. Diagnosis of Creutzfeldt-Jakob disease in Canada: An update on cerebrospinal fluid testing from 2016-2024. Canadian Journal of Neurological Sciences / Journal Canadien des Sciences Neurologiques. Published online 2025:1-23. doi:10.1017/cjn.2025.10088
2. Simon SLR, Peterson A, Phillipson C, Walker J, Richmond M, Jansen G, Knox JD (2020). Prospective study demonstrates utility of EP-QuIC in Creutzfeldt-Jakob Disease diagnoses. Canadian Journal of Neurological Sciences 1-10. 10.1017/cjn.2020.139.
3. Hermann P, Appleby B, Brandel JP, Caughey B, Collins S, Geschwind MD, Green A, Haïk S, Kovacs GG, Ladogana A, Llorens F, Mead S, Nishida N, Pal S, Parchi P, Pocchiari M, Satoh K, Zanusso G, Zerr I. Biomarkers and diagnostic guidelines for sporadic Creutzfeldt-Jakob disease. Lancet Neurol. 2021 Mar;20(3):235-246. doi: 10.1016/S1474-4422(20)30477-4. Erratum in: Lancet Neurol. 2021 Apr;20(4):e3. doi: 10.1016/S1474-4422(21)00069-7. PMID: 33609480; PMCID: PMC8285036.