Second-Generation RT-QuIC Assay for the Diagnosis of Creutzfeldt-Jakob Disease Patients in Brazil

Abstract

The recent development of IQ-CSF, the second generation of real-time quaking-induced conversion (RT-QuIC) using cerebrospinal fluid (CSF), for the diagnosis of Creutzfeldt-Jakob Disease (CJD) represents a major diagnostic advance in the field. Highly accurate results have been reported with encouraging reproducibility among different centers. However, availability is still insufficient, and only a few research centers have access to the method in developing countries. In Brazil, we have had 603 suspected cases of CJD since 2005, when surveillance started. Of these, 404 were undiagnosed. This lack of diagnosis is due, among other factors, to the lack of a reference center for the diagnosis of these diseases in Brazil, resulting in some of these samples being sent abroad for analysis. The aim of this research study is to report the pilot use of IQ-CSF in a small cohort of Brazilian patients with possible or probable CJD, implementing a reference center in the country. We stored CSF samples from patients with possible, probable or genetic CJD (one case) during the time frame of December 2016 through June 2018. All CSF samples were processed according to standardized protocols without access to the clinical data. Eight patients presented to our team with rapidly progressive dementia and typical neurological signs of CJD. We used CSF samples from seven patients with other neurological conditions as negative controls. Five out of seven suspected cases had positive tests; two cases showed inconclusive results. Among controls, there was one false-positive (a CSF sample from a 5-year-old child with leukemia under treatment). The occurrence of a false positive in one of the negative control samples raises the possibility of the presence of interfering components in the CSF sample from patients with non-neurodegenerative pathologies. Our pilot results illustrate the feasibility of having CJD CSF samples tested in Brazilian centers and highlight the importance of interinstitutional collaboration to pursue a higher diagnostic accuracy in CJD in Brazil and Latin America.

Detection of Prions in Brain Homogenates and CSF Samples Using a Second-Generation RT-QuIC Assay: A Useful Tool for Retrospective Analysis of Archived Samples

“…The second-generation RT-QuIC, also known as the IQ assay (Improved QuIC), is a version of the assay with increased sensitivity and significantly shorter time of detection [10]. Almost all human studies utilizing second-generation RT-QuIC have used CSF as the analyte [8][9][10][11][15][16][17][18][19][20][21]. In our retrospective study, we evaluated the second-generation RT-QuIC assay for the analysis of archival post-mortem BH and CSF samples within a TSE patient cohort typical of the Czech Republic [22,23].…”

Utility of Repeat Endpoint Quaking-Induced Conversion Testing in Creutzfeldt–Jakob Disease

“…We hypothesized that repeat CSF testing after 4 weeks could increase the likelihood of a positive EP-QuIC result if the diagnosis was CJD, due to the expected progression of prion burden over time. While the value of repeat RT-QuIC testing in the diagnosis of CJD after an inconclusive result has previously been described, 8 to our knowledge there are no previous reports demonstrating the value of repeat EP-QuIC testing in patients with an initial negative result. The findings of our case suggest that repeat EP-QuIC testing should be considered in patients with an initial negative result if there remains a high index of suspicion for CJD, and may help to ensure accurate patient diagnosis.…”

The importance of ongoing international surveillance for Creutzfeldt–Jakob disease

“…CJD is likely to be under-recognized in nations that lack sophisticated surveillance systems. Several reports from low-income and middle-income nations have described challenges relating to the diagnosis of CJD, including financial constraints, lack of testing facilities, underdeveloped health-care infrastructure, low numbers of neurologists, and regional disparities between rural and urban centres 36 , 38 , 48 , 49 , 279 . Geopolitical instability along with the burden of COVID-19 and other communicable diseases will pose further challenges to the ascertainment of CJD in some of these nations.…”