Cerebrospinal Fluid Real-time Quaking-induced Conversion Research Articles

Sporadic Creutzfeldt-Jakob disease in adults over 80years: a 10-year review of United Kingdom surveillance.

Sporadic Creutzfeldt-Jakob disease (sCJD) is a rapidly progressive neurodegenerative disease with public health implications. Mean age of onset is 68years. Age-specific incidence declines after 80years. This may arise from under-ascertainment or other biological features of the disease. Accurate characterisation of late-onset sCJD is important for early diagnosis, avoiding unnecessary investigations and improving ascertainment for public health purposes. To phenotype the clinical features and investigation profile of sCJD in adults >80years. We analysed all probable and definite sCJD cases identified by the UK National CJD Research & Surveillance Unit over a 10-year period (2011-2021). Individuals were grouped by age of onset. Clinical features and investigation profiles were compared. 10.3% (123/1196) had an age of onset over 80. Median survival was shorter (3.2 vs 4.3months; P < 0.001). Pyramidal signs (48.3% vs 34.2%; P = 0.008) and akinetic mutism (55.1% vs 33.2%; P < 0.001) were more frequent. Psychiatric symptoms (26.3% vs 39.6%; P = 0.01) and cerebellar signs (65.4% vs 78.6%, P = 0.007) were less frequent. Cognitive impairment and myoclonus were highly prevalent regardless of age. Between age groups, the diagnostic sensitivity of cerebrospinal fluid real-time quaking-induced conversion (CSF RT-QuIC) (92.9% vs 91.9%, P = 0.74) was comparable, electroencephalography was superior (41.5% vs 25.4%; P = 0.006) and MRI was inferior (67.8% vs 91.4%; P < 0.001). Late-onset sCJD has distinct clinical features, shorter survival and a different profile of investigation sensitivity. CSF RT-QuIC, MRI brain and specialist CJD review is recommended in older adults with a rapidly progressive neurological disorder. Autopsy is valuable when the cause remains elusive.

α-Synuclein seed amplification assay detects Lewy body co-pathology in autosomal dominant Alzheimer's disease late in the disease course and dependent on Lewy pathology burden.

Amyloid beta and tau pathology are the hallmarks of sporadic Alzheimer's disease (AD) and autosomal dominant AD (ADAD). However, Lewy body pathology (LBP) is found in ≈ 50% of AD and ADAD brains. Using an α-synuclein seed amplification assay (SAA) in cerebrospinal fluid (CSF) from asymptomatic (n=26) and symptomatic (n=27) ADAD mutation carriers, including 12 with known neuropathology, we investigated the timing of occurrence and prevalence of SAA positive reactivity in ADAD in vivo. No asymptomatic participant and only 11% (3/27) of the symptomatic patients tested SAA positive. Neuropathology revealed LBP in 10/12 cases, primarily affecting the amygdala or the olfactory areas. In the latter group, only the individual with diffuse LBP reaching the neocortex showed α-synuclein seeding activity in CSF in vivo. Results suggest that in ADAD LBP occurs later than AD pathology and often as amygdala- or olfactory-predominant LBP, for which CSF α-synuclein SAA has low sensitivity. Cerebrospinal fluid (CSF) real-time quaking-induced conversion (RT-QuIC) detects misfolded α-synuclein in ≈ 10% of symptomatic autosomal dominant Alzheimer's disease (ADAD) patients. CSF RT-QuIC does not detect α-synuclein seeding activity in asymptomatic mutation carriers. Lewy body pathology (LBP) in ADAD mainly occurs as olfactory only or amygdala-predominant variants. LBP develops late in the disease course in ADAD. CSF α-synuclein RT-QuIC has low sensitivity for focal, low-burden LBP.

Performance of a seed amplification assay for misfolded alpha-synuclein in cerebrospinal fluid and brain tissue in relation to Lewy body disease stage and pathology burden

The development of in vitro seed amplification assays (SAA) detecting misfolded alpha-synuclein (αSyn) in cerebrospinal fluid (CSF) and other tissues has provided a pathology-specific biomarker for Lewy body disease (LBD). However, αSyn SAA diagnostic performance in early pathological stages or low Lewy body (LB) pathology load has only been assessed in small cohorts. Moreover, the relationship between SAA kinetic parameters, the number of αSyn brain seeds and the LB pathology burden assessed by immunohistochemistry has never been systematically investigated. We tested 269 antemortem CSF samples and 138 serially diluted brain homogenates from patients with and without neuropathological evidence of LBD in different stages by the αSyn Real-Time Quaking-Induced Conversion (RT-QuIC) SAA. Moreover, we looked for LB pathology by αSyn immunohistochemistry in a consecutive series of 604 Creutzfeldt–Jakob disease (CJD)-affected brains. αSyn CSF RT-QuIC showed 100% sensitivity in detecting LBD in limbic and neocortical stages. The assay sensitivity was significantly lower in patients in early stages (37.5% in Braak 1 and 2, 73.3% in Braak 3) or with focal pathology (50% in amygdala-predominant). The average number of CSF RT-QuIC positive replicates significantly correlated with LBD stage. Brain homogenate RT-QuIC showed higher sensitivity than immunohistochemistry for the detection of misfolded αSyn. In the latter, the kinetic parameter lag phase (time to reach the positive threshold) strongly correlated with the αSyn seed concentration in serial dilution experiments. Finally, incidental LBD prevalence was 8% in the CJD cohort. The present results indicate that (a) CSF RT-QuIC has high specificity and sufficient sensitivity to detect all patients with LB pathology at Braak stages > 3 and most of those at stage 3; (b) brain deposition of misfolded αSyn precedes the formation of LB and Lewy neurites; (c) αSyn SAA provides “quantitative” information regarding the LB pathology burden, with the lag phase and the number of positive replicates being the most promising variables to be used in the clinical setting.

Real-time quaking-induced conversion assay using a small-scale substrate production workflow for the diagnosis of Creutzfeldt-Jakob disease.

The lack of a dedicated surveillance program for prion disease, particularly in low- and middle-income countries (LMICs), has hindered the global effort to address this public health threat. Although cerebrospinal fluid (CSF) Real-time quaking-induced conversion (RT-QuIC) is considered the most reliable test for sporadic Creutzfeldt-Jakob disease (sCJD), its availability in LMICs is limited due to its cost and technical difficulty in generating the recombinant prion protein substrate (recPrP). This study aimed to evaluate the performance of RT-QuIC with recPrP produced in-house through a small-scale method - i.e. the application of reusable pre-packed chromatography columns and subsequent dialysis. Here, CSF specimens from patients suspected of having prion disease were consecutively collected and stored between October 2015 and January 2023. Electronic medical record data were reviewed to clinically classified participants as probable sCJD or non-sCJD. CSF RT-QuIC was performed using in-house recPrP. Its specificity and sensitivity for diagnosing probable sCJD were reported, along with details of other clinical data and investigations. We found that among 39 eligible participants, with a median (interquartile range) age of 64 (56-70) years and 16 (41%) female, 13 had probable sCJD and the remaining 26 unequivocally suffered from non-prion disorders. Magnetic resonance imaging and electroencephalogram were suggestive of sCJD in 100% (13/13) and 46.2% (6/13) of sCJD participants, respectively. RT-QuIC was positive in 12/13 sCJD participants (sensitivity 0.92, 95% confidence interval (CI) 0.67-0.99) and negative in all non-sCJD participants (specificity 1.00, 95%CI 0.87-1.00). CSF tau/p-tau ratio showed sensitivity and specificity of 0.62-1.0 and 0.85-1.0, respectively. In summary, RT-QuIC using recPrP generated through a small-scale workflow demonstrated great performance in detecting sCJD. Given its performance results along with its low cost, this technique could feasibly be implemented in LMICs and potentially be the first step towards establishing local prion disease surveillance programs.

Brain and Cerebrospinal Fluid α-Synuclein Real-Time Quaking-Induced Conversion Identifies Lewy Body Pathology in LRRK2-PD.

The neuropathology of Parkinson's disease (PD) associated with leucine-rich repeat kinase 2 (LRRK2) mutations (LRRK2-PD) is heterogeneous and varies with the type of mutation. There are only a few studies evaluating seeding aggregation assays to detect α-synuclein (α-syn) in patients with LRRK2-PD. We aimed to investigate whether α-syn real-time quaking induced conversion (RT-QuIC) is a sensitive biomarker of synucleinopathy in LRRK2-PD. We studied α-syn RT-QuIC in brain tissue and postmortem ventricular cerebrospinal fluid (CSF) of LRRK2-PD cases with and without Lewy-type pathology. The accuracy of α-syn RT-QuIC in substantia nigra and CSF samples of patients with LRRK2-PD was 100%. The test also obtained 100% sensitivity to detect misfolded α-syn in substantia nigra of cases with idiopathic PD and was negative in the substantia nigra of all the control brains without Lewy-type pathology. Substantia nigra and ventricular CSF RT-QuIC discriminates with high sensitivity and specificity LRRK2 cases with Lewy-type pathology from those without it. RT-QuIC assay could be of particular interest in the selection of cases for clinical trials in this genetic form of PD. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Analysis of Clinical Features, Diagnostic Tests, and Biomarkers in Patients With Suspected Creutzfeldt-Jakob Disease, 2014-2021

Detection of prion proteins in cerebrospinal fluid (CSF) using real-time quaking-induced conversion (RT-QuIC) assays has transformed the diagnostic approach to sporadic Creutzfeldt-Jakob disease (CJD), facilitating earlier and more complete recognition of affected patients. It is unclear how expanded recognition of affected patients may affect the diagnostic and prognostic relevance of clinical features and diagnostic tests historically associated with CJD. To evaluate clinical features and diagnostic testing in patients presenting with CJD and determine the associations of these features with prognosis. This cohort study incorporated data from electronic medical records of patients with CJD treated at Mayo Clinic Enterprise tertiary care centers in Rochester, Minnesota; Jacksonville, Florida; and Scottsdale, Arizona. Participants included patients with definite or probable CJD assessed from 2014 to 2021. Data were analyzed October 2021 to January 2022. Dominant presentation, clinical features, and diagnostic tests associated with CJD. The outcomes of interest were the sensitivity and prognostic value of clinical features and accessible diagnostic tests at presentation with possible CJD. A total of 115 patients were identified, including 40 patients (35%) with definite CJD. Mean (SD) age at symptom onset was 64.8 (9.4) years, and 68 patients were women (59%). The sensitivity of clinical markers (myoclonus) and tests historically considered in patients with suspected CJD was poor (eg, stereotyped electroencephalography anomalies: 17 of 105 patients [16%]; elevated CSF protein 14-3-3 levels: 54 of 90 patients [60%]). By comparison, biomarkers with good diagnostic sensitivity at presentation included RT-QuIC (66 of 71 patients [93%]), CSF total tau (T-tau) level greater than 1149 pg/mL (81 of 92 patients [88%]), and characteristic signal anomalies on magnetic resonance imaging (88 of 115 patients [77%]). Multivariable linear regression confirmed shorter survival in patients with myoclonus (difference, -125.9 [95% CI, -236.3 to -15.5] days; P = .03), visual or cerebellar signs (difference, -180.2 [95% CI, -282.2 to -78.2] days; P < .001), elevated CSF protein 14-3-3 levels (difference, -193 [95% CI, -304.9 to -82.9] days; P < .001), and elevated T-tau level (difference for every 1000 pg/mL elevation, -9.1 [95% CI, -17.7 to -1.0] days; P = .04). These findings suggest that CSF RT-QuIC, elevated CSF T-tau level, and stereotyped magnetic resonance imaging anomalies were associated with the diagnosis of CJD, while other clinical findings (eg, myoclonus), stereotyped electroencephalography anomalies, and CSF protein 14-3-3 levels offered less diagnostic value. Visual or cerebellar features, myoclonus, and CSF 14-3-3 and T-tau levels may be associated with disease duration, justifying continued inclusion in the evaluation of patients suspected to have CJD.

Concordance of cerebrospinal fluid real‐time quaking‐induced conversion across the European Creutzfeldt–Jakob Disease Surveillance Network

Background and purposeCerebrospinal fluid (CSF) real‐time quaking‐induced conversion (RT‐QuIC) has a high degree of sensitivity and specificity for the diagnosis of sporadic Creutzfeldt–Jakob disease (sCJD) and this has led to its being included in revised European CJD Surveillance Network diagnostic criteria for sCJD. As CSF RT‐QuIC becomes more widely established, it is crucial that the analytical performance of individual laboratories is consistent. The aim of this ring‐trial was to ascertain the degree of concordance between European countries undertaking CSF RT‐QuIC.MethodsTen identical CSF samples, seven from probable or neuropathologically confirmed sCJD and three from non‐CJD cases, were sent to 13 laboratories from 11 countries for RT‐QuIC analysis. A range of instrumentation and different recombinant prion protein substrates were used. Each laboratory analysed the CSF samples blinded to the diagnosis and reported the results as positive or negative.ResultsAll 13 laboratories correctly identified five of the seven sCJD cases and the remaining two sCJD cases were identified by 92% of laboratories. Of the two sCJD cases that were not identified by all laboratories, one had a disease duration >26 months with a negative 14‐3‐3, whilst the remaining case had a 4‐month disease duration and a positive 14‐3‐3. A single false positive CSF RT‐QuIC result was observed in this study.ConclusionsThis study shows that CSF RT‐QuIC demonstrates an excellent concordance between centres, even when using a variety of instrumentation, recombinant prion protein substrates and CSF volumes. The adoption of CSF RT‐QuIC by all CJD surveillance centres is recommended.

Validation and Application of Skin RT-QuIC to Patients in China with Probable CJD.

The definite diagnosis of human sporadic Creutzfeldt–Jakob disease (sCJD) largely depends on postmortem neuropathology and PrPSc detection in the brain. The development of real-time quaking-induced conversion (RT-QuIC) of cerebrospinal fluid (CSF) samples makes it possible for premortem diagnosis for sCJD. To test the diagnostic potential of RT-QuIC of skin specimens for probable sCJD, we collected the paired skin and CSF samples from 51 recruited living patients referred to the Chinese CJD surveillance center, including 34 probable sCJD, 14 non-CJD, and 3 genetic prion disease (gPrD). The samples were subjected to RT-QuIC assays using recombinant hamster PrP protein rHaPrP90-231 as the substrate. Using skin RT-QuIC assay, 91.2% (31/34) probable sCJD patients, and 1 T188K genetic CJD (gCJD) cases showed positive prion-seeding activity, while 85.7% (12/14) non-CJD patients were negative. CSF RT-QuIC positive seeding activity was only observed in 14 probable sCJD patients. Analysis of the reactivity of 38 positive skin RT-QuIC tests revealed that the positive rates in the preparations of 10−2, 10−3 and 10−4 diluted skin samples were 88.6% (39/44), 63.6% (28/44), and 25.0% (11/44), respectively. Eleven probable sCJD patients donated two skin specimens collected at different sites simultaneously. Although 95.5% (21/22) skin RT-QuIC elicited positive reaction, the reactivity varied. Our preliminary data indicate high sensitivity and specificity of skin RT-QuIC in prion detection for Chinese probable sCJD and highlight that skin prion-seeding activity is a reliable biomarker for premortem diagnosis of human prion disease.

Human prion diseases.

Prion diseases are rapidly progressive neurodegenerative conditions that can be difficult to diagnose and are transmissible under specific circumstances. The authors will provide background regarding prion disease and focus on diagnostic tools. Prion disease is caused by misfolded prion protein. The three possible causes of prion disease include sporadic (85%), genetic (10-15%), and acquired (<1%). Acquired prion diseases include kuru, iatrogenic, and variant Creutzfeldt-Jakob disease. Prion diseases differ in their clinical manifestation, neuropathology, and diagnostic test results. A variety of recent diagnostic tools have evolved that allow more reliable antemortem diagnosis of prion disease such as brain MRI and cerebrospinal fluid real-time quaking-induced conversion. Special infectivity guidelines must be followed when dealing with central nervous system tissue, but only standard precautions are needed for routine clinical care of patients with prion disease. The only way to definitely diagnose prion disease and determine its type is via neuropathologic examination. However, brain MRI and cerebrospinal fluid real-time quaking-induced conversion have drastically increased diagnostic accuracy and are important tests to use when evaluating patients with suspected prion disease.

RT-QuIC: a new test for sporadic CJD

The diagnosis of sporadic Creutzfeldt-Jakob disease (CJD) can be difficult, but the real-time quaking-induced conversion (RT-QuIC) assays have made a considerable impact on its clinical diagnosis. This technique exploits the...

High diagnostic value of second generation CSF RT-QuIC across the wide spectrum of CJD prions

An early and accurate in vivo diagnosis of rapidly progressive dementia remains challenging, despite its critical importance for the outcome of treatable forms, and the formulation of prognosis. Real-Time Quaking-Induced Conversion (RT-QuIC) is an in vitro assay that, for the first time, specifically discriminates patients with prion disease. Here, using cerebrospinal fluid (CSF) samples from 239 patients with definite or probable prion disease and 100 patients with a definite alternative diagnosis, we compared the performance of the first (PQ-CSF) and second generation (IQ-CSF) RT-QuIC assays, and investigated the diagnostic value of IQ-CSF across the broad spectrum of human prions. Our results confirm the high sensitivity of IQ-CSF for detecting human prions with a sub-optimal sensitivity for the sporadic CJD subtypes MM2C and MM2T, and a low sensitivity limited to variant CJD, Gerstmann-Sträussler-Scheinker syndrome and fatal familial insomnia. While we found no difference in specificity between PQ-CSF and IQ-CSF, the latter showed a significant improvement in sensitivity, allowing prion detection in about 80% of PQ-CSF negative CJD samples. Our results strongly support the implementation of IQ-CSF in clinical practice. By rapidly confirming or excluding CJD with high accuracy the assay is expected to improve the outcome for patients and their enrollment in therapeutic trials.

Diagnostic and prognostic value of human prion detection in cerebrospinal fluid.

Several prion amplification systems have been proposed for detection of prions in cerebrospinal fluid (CSF), most recently, the measurements of prion seeding activity with second-generation real-time quaking-induced conversion (RT-QuIC). The objective of this study was to investigate the diagnostic performance of the RT-QuIC prion test in the broad phenotypic spectrum of prion diseases. We performed CSF RT-QuIC testing in 2,141 patients who had rapidly progressive neurological disorders, determined diagnostic sensitivity and specificity in 272 cases that were autopsied, and evaluated the impact of mutations and polymorphisms in the PRNP gene, and type 1 or type 2 human prions on diagnostic performance. The 98.5% diagnostic specificity and 92% sensitivity of CSF RT-QuIC in a blinded retrospective analysis matched the 100% specificity and 95% sensitivity of a blind prospective study. The CSF RT-QuIC differentiated 94% of cases of sporadic Creutzfeldt-Jakob disease (sCJD) MM1 from the sCJD MM2 phenotype, and 80% of sCJD VV2 from sCJD VV1. The mixed prion type 1-2 and cases heterozygous for codon 129 generated intermediate CSF RT-QuIC patterns, whereas genetic prion diseases revealed distinct profiles for each PRNP gene mutation. The diagnostic performance of the improved CSF RT-QuIC is superior to surrogate marker tests for prion diseases such as 14-3-3 and tau proteins, and together with PRNP gene sequencing the test allows the major prion subtypes to be differentiated in vivo. This differentiation facilitates prediction of the clinicopathological phenotype and duration of the disease-two important considerations for envisioned therapeutic interventions. ANN NEUROL 2017;81:79-92.

Diagnosis of Human Prion Disease Using Real-Time Quaking-Induced Conversion Testing of Olfactory Mucosa and Cerebrospinal Fluid Samples

Early and accurate in vivo diagnosis of Creutzfeldt-Jakob disease (CJD) is necessary for quickly distinguishing treatable from untreatable rapidly progressive dementias and for future therapeutic trials. This early diagnosis is becoming possible using the real-time quaking-induced conversion (RT-QuIC) seeding assay, which detects minute amounts of the disease-specific pathologic prion protein in cerebrospinal fluid (CSF) or olfactory mucosa (OM) samples. To develop an algorithm for accurate and early diagnosis of CJD by using the RT-QuIC assay on CSF samples, OM samples, or both. In this case-control study, samples of CSF and OM were collected from 86 patients with a clinical diagnosis of probable (n = 51), possible (n = 24), or suspected (n = 11) CJD and 104 negative control samples (54 CSF and 50 OM). The CSF and OM samples were analyzed using conventional RT-QuIC. The CSF samples underwent further testing using improved RT-QuIC conditions. In addition, the diagnostic performance of a novel, easy-to-use, gentle flocked swab for sampling of OM was evaluated. Data were collected from January 1 to June 30, 2015. Correlations between RT-QuIC results and the final diagnosis of recruited patients. Among the 86 patients (37 men [43%] and 49 women [57%]; mean [SD] age, 65.7 [11.5] years) included for analysis, all 61 patients with sporadic CJD had positive RT-QuIC findings using OM or CSF samples or both for an overall RT-QuIC diagnostic sensitivity of 100% (95% CI, 93%-100%). All patients with a final diagnosis of non-prion disease (71 CSF and 67 OM samples) had negative RT-QuIC findings for 100% specificity (95% CI, 94%-100%). Of 8 symptomatic patients with various mutations causing CJD or Gerstmann-Sträussler-Scheinker syndrome, 6 had positive and 2 had negative RT-QuIC findings for a sensitivity of 75% (95% CI, 36%-96%). A proposed diagnostic algorithm for sporadic CJD combines CSF and OM RT-QuIC testing to provide virtually 100% diagnostic sensitivity and specificity in the clinical phase of the disease.

Cerebrospinal fluid real-time quaking-induced conversion is a robust and reliable test for sporadic creutzfeldt-jakob disease: An international study.

Real‐time quaking‐induced conversion (RT‐QuIC) has been proposed as a sensitive diagnostic test for sporadic Creutzfeldt–Jakob disease; however, before this assay can be introduced into clinical practice, its reliability and reproducibility need to be demonstrated. Two international ring trials were undertaken in which a set of 25 cerebrospinal fluid samples were analyzed by a total of 11 different centers using a range of recombinant prion protein substrates and instrumentation. The results show almost complete concordance between the centers and demonstrate that RT‐QuIC is a suitably reliable and robust technique for clinical practice. Ann Neurol 2016;80:160–165