Application of real-time quaking-induced conversion in Creutzfeldt-Jakob disease surveillance

Isolated CSF RT-QuIC positivity associates with a less aggressive disease course and decreased levels of neuronal/glial damage biomarkers in patients with sporadic Creutzfeldt-Jakob disease

Discrepancies in results between cerebrospinal fluid (CSF) 14-3-3 protein and prion protein detection using real-time quaking-induced conversion (RT-QuIC) might limit the confidence in ante-mortem clinical diagnosis of sporadic Creutzfeldt-Jakob disease (sCJD). We aimed to evaluate the concordance and diagnostic performance of 14-3-3 protein and RT-QuIC in a real clinical practice cohort, and to analyze neuronal/glial damage biomarkers in sCJD patients based on their diagnostic assay results. A retrospective multicentre study was conducted on 157 suspected sCJD patients from 38 Spanish hospitals in a 4-year period. CSF 14-3-3 protein and RT-QuIC were simultaneously evaluated in a single laboratory. A diagnosis of probable sCJD was established in 63 patients (40.1%), of which 12 (19.0%) were ultimately diagnosed with definite sCJD. Forty-one sCJD patients (65.1%) were positive for both 14-3-3 protein and RT-QuIC, 17 (27.0%) isolated positive for RT-QuIC, and 5 (7.9%) isolated positive for 14-3-3 protein. RT-QuIC demonstrated higher sensitivity (92.1%) and specificity (98.9%) compared to 14-3-3 (73.0% and 62.8%) for the diagnosis of sCJD. Isolated RT-QuIC positivity was associated with longer disease duration (median: 10.5 months, IQR: 8.8-15.7), higher frequency of Met/Val cases (75.0%), lower prevalence of periodic sharp-wave complexes (5.9%), and lower levels of GFAP (3967.4 pg/mL), UCH-L1 (2218.1 pg/mL), and t-Tau (228.8 pg/mL) compared to double-positive and isolated 14-3-3-positive patients. In conclusion, CSF RT-QuIC is a highly specific and sensitive biomarker for ante-mortem sCJD diagnosis and should be considered as the preferred CSF ancillary test. Isolated RT-QuIC positivity indicates a less aggressive biological disease in sCJD patients.

Creutzfeldt-Jakob disease and other prion diseases

Prion diseases share common clinical and pathological characteristics such as spongiform neuronal degeneration and deposition of an abnormal form of a host-derived protein, termed prion protein. The characteristic features of prion diseases are long incubation times, short clinical courses, extreme resistance of the transmissible agent to degradation and lack of nucleic acid involvement. Sporadic and genetic forms of prion diseases occur worldwide, of which genetic forms are associated with mutations in PRNP. Human to human transmission of these diseases has occurred due to iatrogenic exposure, and zoonotic forms of prion diseases are linked to bovine disease. Significant progress has been made in the diagnosis of these disorders. Clinical tools for diagnosis comprise brain imaging and cerebrospinal fluid tests. Aggregation assays for detection of the abnormally folded prion protein have a clear potential to diagnose the disease in peripherally accessible biofluids. After decades of therapeutic nihilism, new treatment strategies and clinical trials are on the horizon. Although prion diseases are relatively rare disorders, understanding their pathogenesis and mechanisms of prion protein misfolding has significantly enhanced the field in research of neurodegenerative diseases.

Fast-track neuropathological screening for neurodegenerative diseases

Background: The postmortem diagnostic of individuals having suffered presumptive neurodegenerative disease comprises exclusion of a prion disease, extensive brain sampling and histopathological evaluation, which are resource-intensive and time consuming. To exclude prion disease and to achieve prompt accurate preliminary diagnosis, we developed a fast-track procedure for the histopathological assessment of brains from patients with suspected neurodegenerative disease. Methods: Based on the screening of two brain regions (frontal cortex and cerebellum) with H&E and six immunohistochemical stainings in 133 brain donors, a main histopathological diagnosis was established and compared to the final diagnosis made after a full histopathological work-up according to our brain bank standard procedure. Results: In over 96 % of cases there was a concordance between the fast-track and the final main neuropathological diagnosis. A prion disease was identified in four cases without prior clinical suspicion of a prion infection. Conclusion: The fast-track screening approach relying on two defined, easily accessible brain regions is sufficient to obtain a reliable tentative main diagnosis in individuals with neurodegenerative disease and thus allows for a prompt feedback to the physicians. However, a more thorough histological work-up taking into account the clinical history and the working diagnosis from fast-track screening is necessary for accurate staging and for assessment of co-pathologies.

Creutzfeldt - Jakob disease: clinical cases

A 68 y.o. woman delivered to the emergency department with severe speech impairment in a somnolent state - 13 points Glasgow Coma Scale. Her relatives described a clinical manifestation: rapidly progressive dementia, visual disturbances, abnormal gait and coordination, retrograde amnesia. A 67 y. o. man delivered to the emergency department with headache, vertigo, abnormal gait and coordination, progressive extremities weakness, disorientation, memory and concentration impairment. His relatives told about extremely rapidly progression of symptoms during last three months. First clinical case presents a Heidenhain variant, second case - Brownell - Oppenheimer variant.

Diagnostic accuracy of diffusion-weighted imaging in variant Creutzfeldt-Jakob disease

PURPOSE

This study sought to investigate the diagnostic sensitivity of diffusion-weighted imaging (DWI) in variant Creutzfeldt-Jakob disease (vCJD), a prion disease with significant public health implications on account of its transmissibility. The importance of this research stemmed from the first neuropathologically confirmed vCJD case in a PRNP heterozygous individual in 2016, which displayed DWI features typical of sporadic CJD (sCJD). The case was classified as 'probable' sCJD in life, predominantly based on these imaging findings. While DWI has proven valuable in diagnosing sCJD, its utility in vCJD diagnosis remains unclear.

METHODS

DWI and Fluid-attenuated inversion recovery (FLAIR) images from probable and definite vCJD cases referred to the National CJD Research and Surveillance Unit (NCJDRSU) were independently analysed by an expert neuroradiologist. Scans were reviewed within a mixed cohort of CJD cases including definite sCJD and non-CJD controls.

RESULTS

FLAIR sequences demonstrated greater sensitivity in identifying the pulvinar sign in vCJD compared to DWI (73% vs 41%, p-value <0.001). Basal ganglia hyperintensities were more prevalent in DWI (84%) than FLAIR (64%), and cortical hyperintensities were exclusive to DWI (24%). The pulvinar sign showed a specificity of 98% for vCJD and was rare in sCJD.

CONCLUSION

DWI showed reduced sensitivity compared to FLAIR imaging in detecting the pulvinar sign in vCJD. Conversely, DWI can more distinctively identify basal ganglia and cortical hyperintensities, thus leading to imaging patterns more characteristic of sCJD. Therefore, DWI should be cautiously interpreted in vCJD diagnosis, with axial FLAIR potentially providing a more precise evaluation of the pulvinar sign.

The advances in the early and accurate diagnosis of Creutzfeldt-Jakob disease and other prion diseases: where are we today?

INTRODUCTION

Before the introduction of MRI diffusion-weighted images (DWI), the diagnosis of Creutzfeldt-Jakob disease (CJD) relied upon nonspecific findings including clinical symptoms, EEG abnormalities, and elevated levels of cerebrospinal fluid 14-3-3 protein. Subsequently, the use of DWI has improved diagnostic accuracy, but it sometimes remains difficult to differentiate CJD from encephalitis, epilepsy, and other dementing disorders. The revised diagnostic criteria include real-time quaking-induced conversion (RT-QuIC), detecting small amounts of CJD-specific prion protein, and clinically sensitive DWI. Combining these techniques has further improved diagnostic accuracy, enabling earlier diagnosis.

AREAS COVERED

Herein, the authors review the recent advances in diagnostic methods and revised diagnostic criteria for sporadic CJD. They also discuss other prion diseases, such as variant CJD and chronic wasting disease, where the emergence of new types is a concern.

EXPERT OPINION

Despite improvements in diagnostic methods and criteria, some subtypes of prion disease are still difficult to diagnose, and even the diagnosis using the most innovative RT-QuIC test remains a challenge in terms of accuracy and standardization. However, these revised criteria can be adapted to the emergence of new types of prion diseases. It is essential to continue careful surveillance and update information on the latest prion disease phenotypes.