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.

Levels of plasma brain-derived tau and p-tau181 in Alzheimer's disease and rapidly progressive dementias.

INTRODUCTION: Rapidly progressive dementias (RPDs) are a group of neurological disorders characterized by a rapid cognitive decline. The diagnostic value of blood-based biomarkers for Alzheimer's disease (AD) in RPD has not been fully explored. METHODS: We measured plasma brain-derived tau (BD-tau) and p-tau181 in 11 controls, 15 AD patients, and 33 with RPD, of which 19 were Creutzfeldt-Jakob disease (CJD). RESULTS: Plasma BD-tau differentiated AD from RPD and controls (p = 0.002 and p = 0.03, respectively), while plasma and cerebrospinal fluid (CSF) p-tau181 distinguished AD from RPD (p < 0.001) but not controls from RPD (p > 0.05). The correlation of CSF t-tau with plasma BD-tau was stronger (r = 0.78, p < 0.001) than the correlation of CSF and plasma p-tau181 (r = 0.26, p = 0.04). The ratio BD-tau/p-tau181 performed equivalently to the CSF t-tau/p-tau181 ratio, differentiating AD from CJD (p < 0.0001). DISCUSSION: Plasma BD-tau and p-tau181 mimic their corresponding cerebrospinal fluid (CSF) markers. P-tau significantly increased in AD but not in RPD. Plasma BD-tau, like CSF t-tau, increases according to neurodegeneration intensity.

Rapidly progressive dementia due to intravascular lymphoma: A prion disease reference center experience.

BACKGROUND: Intravascular large B-cell lymphoma (IVLBCL) is a rare extranodal lymphoma that is characterized by the selective growth of neoplastic cells in blood vessels, representing a potentially treatable cause of rapidly progressive dementia (RPD). Given its diverse clinical and instrumental presentation, it is often misdiagnosed with more common RPD causes, for example, Creutzfeldt-Jakob disease (CJD) or vascular dementia. METHODS: This study presents the clinical and histopathological characteristics of four IVLBCL cases that we diagnosed post-mortem over 20 years among over 600 brain samples received as suspected CJD cases at our prion disease reference center. RESULTS: Our patients exhibited various presenting symptoms, including behavioral disturbances, disorientation, and alertness fluctuations. The diagnostic tests performed at the time, including blood work, cerebrospinal fluid (CSF) analyses, electroencephalography, and neuroimaging, yielded nonspecific and occasionally misleading results. Consequently, the patients were repeatedly diagnosed as variably having CJD, epilepsy, vascular dementia, and encephalitis. The stored CSF samples of two patients tested negative at prion real-time quaking-induced conversion (RT-QuIC), which we performed afterwards for research purposes. Neuropathological analysis revealed a differential involvement of various brain areas, with frontotemporal neocortices being the most affected. CONCLUSIONS: Our results confirm the significant clinical and instrumental heterogeneity of IVLBCL. Neuropathological evidence of the preferential involvement of frontotemporal neocortices, potentially conditioning the clinical phenotype, could be relevant to reach an early diagnosis. Finally, given the therapeutic implications of its misdiagnosis with CJD, we emphasize the utility of prion RT-QuIC as a test for ruling out CJD in these patients.

Diagnostic and prognostic value of cerebrospinal fluid SNAP-25 and neurogranin in Creutzfeldt-Jakob disease in a clinical setting cohort of rapidly progressive dementias.

BACKGROUND: The levels of synaptic markers synaptosomal-associated protein 25 (SNAP-25) and neurogranin (Ng) have been shown to increase early in the cerebrospinal fluid (CSF) of patients with Creutzfeldt-Jakob disease (CJD) and to have prognostic potential. However, no validation studies assessed these biomarkers' diagnostic and prognostic value in a large clinical setting cohort of rapidly progressive dementia. METHODS: In this retrospective study, using commercially available immunoassays, we measured the levels of SNAP-25, Ng, 14-3-3, total-tau (t-tau), neurofilament light chain (NfL), and phospho-tau181 (p-tau) in CSF samples from consecutive patients with CJD (n = 220) or non-prion rapidly progressive dementia (np-RPD) (n = 213). We evaluated and compared the diagnostic accuracy of each CSF biomarker and biomarker combination by receiver operating characteristics curve (ROC) analyses, studied SNAP-25 and Ng CSF concentrations distribution across CJD subtypes, and estimated their association with survival using multivariable Cox regression analyses. RESULTS: CSF SNAP-25 and Ng levels were higher in CJD than in np-RPD (SNAP-25: 582, 95% CI 240-1250 vs. 115, 95% CI 78-157 pg/ml, p < 0.0001; Ng: 841, 95% CI 411-1473 vs. 390, 95% CI 260-766 pg/ml, p < 0.001). SNAP-25 diagnostic accuracy (AUC 0.902, 95% CI 0.873-0.931) exceeded that of 14-3-3 (AUC 0.853, 95% CI 0.816-0.889), t-tau (AUC 0.878, 95% CI 0.845-0.901), and the t-tau/p-tau ratio (AUC 0.884, 95% CI 0.851-0.916). In contrast, Ng performed worse (AUC 0.697, 95% CI 0.626-0.767) than all other surrogate biomarkers, except for NfL (AUC 0.649, 95% CI 0.593-0.705). SNAP-25 maintained a relatively high diagnostic value even for atypical CJD subtypes (AUC 0.792, 95% CI 0.729-0.854). In Cox regression analyses, SNAP-25 levels were significantly associated with survival in CJD (hazard ratio [HR] 1.71 95% CI 1.40-2.09). Conversely, Ng was associated with survival only in the most rapidly progressive CJD subtypes (sCJD MM(V)1 and gCJD M1) (HR 1.81 95% CI 1.21-2.93). CONCLUSIONS: In the clinical setting, CSF SNAP-25 is a viable alternative to t-tau, 14-3-3, and the t-tau/p-tau ratio in discriminating the CJD subtypes from other RPDs. Additionally, SNAP-25 and, to a lesser extent, Ng predict survival in CJD, showing prognostic power in the range of CSF t-tau/14-3-3 and NfL, respectively.

High diagnostic performance of plasma and cerebrospinal fluid beta-synuclein for sporadic Creutzfeldt-Jakob disease.

Beta-synuclein is a promising cerebrospinal fluid and blood biomarker of synaptic damage. Here we analysed its accuracy in the discrimination between sporadic Creutzfeldt-Jakob disease (n = 150) and non-prion rapidly progressive dementias (n = 106). In cerebrospinal fluid, beta-synuclein performed better than protein 14-3-3 (AUC 0.95 vs. 0.89) and, to a lesser extent, than total tau (AUC 0.92). Further, the diagnostic value of plasma beta-synuclein (AUC 0.91) outperformed that of plasma tau (AUC 0.79) and neurofilament light chain protein (AUC 0.65) and was comparable to that of cerebrospinal fluid biomarkers. Beta-synuclein might represent the first highly accurate blood biomarker for the diagnosis of sporadic Creutzfeldt-Jakob disease.

Diagnostic value of plasma p-tau181, NfL, and GFAP in a clinical setting cohort of prevalent neurodegenerative dementias.

BACKGROUND: Increasing evidence supports the use of plasma biomarkers of neurodegeneration and neuroinflammation to screen and diagnose patients with dementia. However, confirmatory studies are required to demonstrate their usefulness in the clinical setting. METHODS: We evaluated plasma and cerebrospinal fluid (CSF) samples from consecutive patients with frontotemporal dementia (FTD) (n = 59), progressive supranuclear palsy (PSP) (n = 31), corticobasal syndrome (CBS) (n = 29), dementia with Lewy bodies (DLB) (n = 49), Alzheimer disease (AD) (n = 97), and suspected non-AD physiopathology (n = 51), as well as plasma samples from 60 healthy controls (HC). We measured neurofilament light chain (NfL), phospho-tau181 (p-tau181), and glial fibrillary acid protein (GFAP) using Simoa (all plasma biomarkers and CSF GFAP), CLEIA (CSF p-tau181), and ELISA (CSF NfL) assays. Additionally, we stratified patients according to the A/T/N classification scheme and the CSF α-synuclein real-time quaking-induced conversion assay (RT-QuIC) results. RESULTS: We found good correlations between CSF and plasma biomarkers for NfL (rho = 0.668, p < 0.001) and p-tau181 (rho = 0.619, p < 0.001). Plasma NfL was significantly higher in disease groups than in HC and showed a greater increase in FTD than in AD [44.9 (28.1-68.6) vs. 21.9 (17.0-27.9) pg/ml, p < 0.001]. Conversely, plasma p-tau181 and GFAP levels were significantly higher in AD than in FTD [3.2 (2.4-4.3) vs. 1.1 (0.7-1.6) pg/ml, p < 0.001; 404.7 (279.7-503.0) vs. 198.2 (143.9-316.8) pg/ml, p < 0.001]. GFAP also allowed discriminating disease groups from HC. In the distinction between FTD and AD, plasma p-tau181 showed better accuracy (AUC 0.964) than NfL (AUC 0.791) and GFAP (AUC 0.818). In DLB and CBS, CSF amyloid positive (A+) subjects had higher plasma p-tau181 and GFAP levels than A- individuals. CSF RT-QuIC showed positive α-synuclein seeding activity in 96% DLB and 15% AD patients with no differences in plasma biomarker levels in those stratified by RT-QuIC result. CONCLUSIONS: In a single-center clinical cohort, we confirm the high diagnostic value of plasma p-tau181 for distinguishing FTD from AD and plasma NfL for discriminating degenerative dementias from HC. Plasma GFAP alone differentiates AD from FTD and neurodegenerative dementias from HC but with lower accuracy than p-tau181 and NfL. In CBS and DLB, plasma p-tau181 and GFAP levels are significantly influenced by beta-amyloid pathology.