title: Endpoint Quaking-Induced Conversion: a Sensitive, Specific, and High-Throughput Method for Antemortem Diagnosis of Creutzfeldt-Jacob Disease.
abstract: The Prion Laboratory Section of the Public Health Agency of Canada supports heath care professionals dealing with patients suspected to have Creutzfeldt-Jakob disease (CJD) by testing cerebrospinal fluid (CSF) for protein markers of CJD. To better serve Canadian diagnostic requirements, a quaking-induced conversion (QuIC)-based assay has been added to the test panel. The QuIC tests exploit the ability of disease-associated prion protein, found in the CSF of a majority of CJD patients, to convert a recombinant prion protein (rPrP) into detectable amounts of a misfolded, aggregated form of rPrP. The rPrP aggregates interact with a specific dye, causing a measurable change in the dye's fluorescence emission spectrum. Optimal test and analysis parameters were empirically determined. Taking both practical and performance considerations into account, an endpoint QuIC (EP-QuIC) configuration was chosen. EP-QuIC uses a thermo-mixer to perform the shaking necessary to produce the quaking-induced conversions. Fluorescence readings are obtained from a microwell fluorescence reader only at the beginning and the end of EP-QuIC reactions. Samples for which the relative fluorescence unit ratio between the initial and final readings represent a ≥4 increase in signal intensity in at least two of the three replicates are classified as positive. A retrospective analysis of 91 CSF samples that included 45 confirmed cases of CJD and 46 non-CJD cases was used to estimate the performance characteristics of the EP-QuIC assay. The diagnostic sensitivity and specificity of the EP-QuIC test of this set of samples were 98 and 91%, respectively.
authors.affiliation: National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg, Manitoba, Canada keding.cheng@phac-aspc.gc.ca david.knox@phac-aspc.gc.ca.|Department of Human Anatomy and Cell Sciences, Faculty of Medicine, University of Manitoba, Winnipeg, Manitoba, Canada.
authors.forename: Keding
authors.initials: K
authors.lastname: Cheng
authors.affiliation: National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg, Manitoba, Canada.
authors.forename: Robert
authors.initials: R
authors.lastname: Vendramelli
authors.affiliation: National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg, Manitoba, Canada.
authors.forename: Angela
authors.initials: A
authors.lastname: Sloan
authors.affiliation: National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg, Manitoba, Canada.
authors.forename: Brooks
authors.initials: B
authors.lastname: Waitt
authors.affiliation: National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg, Manitoba, Canada.
authors.forename: Lisa
authors.initials: L
authors.lastname: Podhorodecki
authors.affiliation: National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg, Manitoba, Canada.
authors.forename: Debra
authors.initials: D
authors.lastname: Godal
authors.affiliation: National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg, Manitoba, Canada keding.cheng@phac-aspc.gc.ca david.knox@phac-aspc.gc.ca.|Department of Medical Microbiology, Faculty of Medicine, University of Manitoba, Winnipeg, Manitoba, Canada.
authors.forename: J David
authors.initials: JD
authors.lastname: Knox
mesh_terms: D002170:Canada; D002555:Cerebrospinal Fluid / Q000737:chemistry; D007562:Creutzfeldt-Jakob Syndrome / Q000175:diagnosis*; D003933:Diagnosis; D003955:Diagnostic Tests, Routine / Q000379:methods*; D006801:Humans; D000072002:Prion Proteins / Q000134:cerebrospinal fluid*; D012189:Retrospective Studies; D012680:Sensitivity and Specificity
chemical_list: D000072002:Prion Proteins