Joery Goossens

Cerebrospinal Fluid P-Tau181P: Biomarker for Improved Differential Dementia Diagnosis.

The goal of this study is to investigate the value of tau phosphorylated at threonine 181 (P-tau181P) in the Alzheimer’s disease (AD) cerebrospinal fluid (CSF) biomarker panel for differential dementia diagnosis in autopsy confirmed AD and non-AD patients. The study population consisted of 140 autopsy confirmed AD and 77 autopsy confirmed non-AD dementia patients. CSF concentrations of amyloid-β peptide of 42 amino acids (Aβ1–42), total tau protein (T-tau), and P-tau181P were determined with single analyte ELISA-kits (INNOTEST®, Fujirebio, Ghent, Belgium). Diagnostic accuracy was assessed through receiver operating characteristic (ROC) curve analyses to obtain area under the curve (AUC) values and to define optimal cutoff values to discriminate AD from pooled and individual non-AD groups. ROC curve analyses were only performed on biomarkers and ratios that differed significantly between the groups. Pairwise comparison of AUC values was performed by means of DeLong tests. The Aβ1–42/P-tau181P ratio (AUC = 0.770) performed significantly better than Aβ1–42 (AUC = 0.677, P = 0.004), T-tau (AUC = 0.592, P < 0.001), and Aβ1–42/T-tau (AUC = 0.678, P = 0.001), while P-tau181P (AUC = 0.720) performed significantly better than T-tau (AUC = 0.592, P < 0.001) to discriminate between AD and the pooled non-AD group. When comparing AD and the individual non-AD diagnoses, Aβ1–42/P-tau181P (AUC = 0.894) discriminated AD from frontotemporal dementia significantly better than Aβ1–42 (AUC = 0.776, P = 0.020) and T-tau (AUC = 0.746, P = 0.004), while P-tau181P/T-tau (AUC = 0.958) significantly improved the differentiation between AD and Creutzfeldt-Jakob disease as compared to Aβ1–42 (AUC = 0.688, P = 0.004), T-tau (AUC = 0.874, P = 0.040), and Aβ1–42/P-tau181P (AUC = 0.760, P = 0.003). In conclusion, this study demonstrates P-tau181P is an essential component of the AD CSF biomarker panel, and combined assessment of Aβ1–42, T-tau, and P-tau181P renders, to present date, the highest diagnostic power to discriminate between AD and non-AD dementias.

Diagnostic Impact of Cerebrospinal Fluid Biomarker (Pre-)Analytical Variability in Alzheimer’s Disease

Intra- and inter-laboratory variability of cerebrospinal fluid (CSF) biomarker analyses remains an important issue. We investigated the clinical-diagnostic impact of CSF biomarker concentration shifts in mild cognitive impairment (MCI) and autopsy-confirmed Alzheimer’s disease (AD) dementia patients. MCI patients (n = 85), autopsy-confirmed AD dementia patients (n = 72), and cognitively healthy controls (n = 100) were included in this prospective, longitudinal study. AD dementia patients were followed up until death, and controls were included from 1992 until 2003. In-house validated cutoff values of biomarkers were applied: Aβ1-42 <638.5 pg/mL, T-tau>296.5 pg/mL, P-tau181P >56.5 pg/mL. Both increments and decrements (from ± 5% to ± 40% ) were added to the true (=observed) CSF biomarker values, imitating the anticipated differences in biomarker concentrations. Within certain limits, the clinical diagnostic performance of AD CSF biomarkers remains largely unchanged and clinical diagnostic accuracy deviated less than 8.2% from the reference when concentration shifts ranging between –20% and +20% were added to one of the three CSF biomarkers in MCI and autopsy-confirmed AD patients. Notwithstanding the fact that (pre- and post-)analytical parameters can affect the clinical classification, the present exploratory study provides evidence that for a specific context of use, the impact on clinical accuracy of biomarker concentration shifts might be lower than originally expected. In conclusion, induced shifts of ±20% in only one of the three biomarkers has limited impact on the clinical accuracy of AD CSF biomarkers in MCI and autopsy-confirmed AD patients when using the IWG-2 criteria.

A Decade of Cerebrospinal Fluid Biomarkers for Alzheimer’s Disease in Belgium

During the past ten years, over 5,000 cerebrospinal fluid (CSF) samples were analyzed at the Reference Center for Biological Markers of Dementia (BIODEM), UAntwerp, for core Alzheimers disease (AD) CSF biomarkers: amyloid-β peptide of 42 amino acids (Aβ1-42), total tau protein (T-tau), and tau phosphorylated at threonine 181 (P-tau181P). CSF biomarker analyses were performed using single-analyte ELISA kits. In-house validated cutoff values were applied: Aβ1-42 <638.5 pg/mL, T-tau >296.5 pg/mL, P-tau181P >56.5 pg/mL. A CSF biomarker profile was considered to be suggestive for AD if the CSF Aβ1-42 concentration was below the cutoff, in combination with T-tau and/or P-tau181P values above the cutoff (IWG2 criteria for AD). Biomarker analyses were requested for following clinical indications: 1) neurochemical confirmation of AD in case of clinical AD, 2) neurochemical confirmation of AD in case of doubt between AD and a non-AD dementia, 3) neurochemical diagnosis of prodromal AD in case of mild cognitive impairment, 4) neurochemical confirmation of AD in case of psychiatric symptoms (like depression, psychosis), or 5) other clinical indications. During these ten years, the number of yearly referred samples increased by 238% and clinical indications for referral showed a shift from neurochemical confirmation of AD in case of clinical AD to differential dementia diagnosis in case of doubt between AD and a non-AD dementia. Four percent of the patients also had a postmortem neuropathological examination. Together, these biomarker data were the basis for several research papers, and significantly contributed to the validation of these biomarkers in autopsy-confirmed subjects.

TDP-43 as a possible biomarker for frontotemporal lobar degeneration : a systematic review of existing antibodies

Frontotemporal lobar degeneration (FTLD) is one of the leading causes of dementia after Alzheimer’s disease. A high-ranking candidate to become a diagnostic marker for a major pathological subtype of FTLD is the transactive response DNA binding protein of 43 kDa (TDP-43). The main objective is to elucidate which antibodies are specific for pathological TDP-43, with special interest in its modified isoforms. Indeed, TDP-43 has been shown to be hyperphosphorylated and truncated in disease. A secondary objective is to review existing immunoassays that quantify TDP-43 in biofluids. A systematic review of literature was performed by searching PubMed and Web of Science using predefined keywords. Of considered research papers the methods section was reviewed to select publications that enabled us to answer our learning objective. After quality assessment, antibody characteristics and related outcomes were extracted. We identified a series of well-characterized antibodies based on a scoring system that assessed the ability of each antibody to detect TDP-43 pathology. A selection of 29 unique antibodies was made comprising 10 high-ranking antibodies which were reported multiple times to detect TDP-43 pathology in both immunostaining and immunoblotting experiments and 19 additional antibodies which detected TDP-43 pathology but were only scored once. This systematic review provides an overview of antibodies that are reported to detect pathological TDP-43. These antibodies can be used in future studies of TDP-43 proteinopathies. Additionally, selected antibodies hold the potential to be used in the development of novel immunoassays for the quantification of TDP-43 in biofluids, as a possible biomarker for FTLD-TDP.

Selecting Aβ isoforms for an Alzheimer's disease cerebrospinal fluid biomarker panel

Although the core cerebrospinal fluid Alzheimers disease (AD) biomarkers amyloid-β (Aβ1-42) and tau show a high diagnostic accuracy, there are still limitations due to overlap in the biomarker levels with other neurodegenerative and dementia disorders. During Aβ1-42 production and clearance in the brain, several other Aβ peptides and amyloid precursor protein fragments are formed that could potentially serve as biomarkers for this ongoing disease process. Therefore, this review will present the current status of the findings for amyloid precursor protein and Aβ peptide isoforms in AD and clinically related disorders. In conclusion, adding new Aβ isoforms to the AD biomarker panel may improve early differential diagnostic accuracy and increase the cerebrospinal fluid biomarker concordance with AD neuropathological findings in the brain.

Diagnostic value of cerebrospinal fluid tau, neurofilament, and progranulin in definite frontotemporal lobar degeneration

BackgroundWe explored the diagnostic performance of cerebrospinal fluid (CSF) biomarkers in allowing differentiation between frontotemporal lobar degeneration (FTLD) and Alzheimer’s disease (AD), as well as between FTLD pathological subtypes.MethodsCSF levels of routine AD biomarkers (phosphorylated tau (p-tau181), total tau (t-tau), and amyloid-beta (Aβ)1–42) and neurofilament proteins, as well as progranulin levels in both CSF and serum were quantified in definite FTLD (n = 46), clinical AD (n = 45), and cognitively healthy controls (n = 20). FTLD subgroups were defined by genetic carrier status and/or postmortem neuropathological confirmation (FTLD-TDP: n = 34, including FTLD-C9orf72: n = 19 and FTLD-GRN: n = 9; FTLD-tau: n = 10).ResultsGRN mutation carriers had significantly lower progranulin levels compared to other FTLD patients, AD, and controls. Both t-tau and p-tau181 were normal in FTLD patients, even in FTLD-tau. Aβ1–42 levels were very variable in FTLD. Neurofilament light chain (Nf-L) was significantly higher in FTLD compared with AD and controls. The reference logistic regression model based on the established AD biomarkers could be improved by the inclusion of CSF Nf-L, which was also important for the differentiation between FTLD and controls. Within the FTLD cohort, no significant differences were found between FTLD-TDP and FTLD-tau, but GRN mutation carriers had higher t-tau and Nf-L levels than C9orf72 mutation carriers and FTLD-tau patients.ConclusionsThere is an added value for Nf-L in the differential diagnosis of FTLD. Progranulin levels in CSF depend on mutation status, and GRN mutation carriers seem to be affected by more severe neurodegeneration.

EEG Dominant Frequency Peak Differentiates Between Alzheimer's Disease and Frontotemporal Lobar Degeneration.

We investigated the power of EEG as biomarker in differential diagnosis of Alzheimers disease (AD) and frontotemporal lobar degeneration (FTLD). EEG was recorded from 106 patients with AD or FTLD, of which 37 had a definite diagnosis, and 40 controls. Dominant frequency peaks were extracted for all 19 channels, for each subject. The average frequency of the largest dominant frequency peaks (maxpeak) was significantly lower in AD than FTLD patients and controls. Based on ROC analysis, classification could be made with diagnostic accuracy of 78.9%. Our findings show that quantitative analysis of EEG maxpeak frequency is an easy and useful measure for differential dementia diagnosis.

EEG DOMINANT FREQUENCY PEAK DIFFERENTIATES BETWEEN ALZHEIMER'S DISEASE AND FRONTOTEMPORAL LOBAR DEGENERATION

We investigated the power of EEG as biomarker in differential diagnosis of Alzheimers disease (AD) and frontotemporal lobar degeneration (FTLD). EEG was recorded from 106 patients with AD or FTLD, of which 37 had a definite diagnosis, and 40 controls. Dominant frequency peaks were extracted for all 19 channels, for each subject. The average frequency of the largest dominant frequency peaks (maxpeak) was significantly lower in AD than FTLD patients and controls. Based on ROC analysis, classification could be made with diagnostic accuracy of 78.9%. Our findings show that quantitative analysis of EEG maxpeak frequency is an easy and useful measure for differential dementia diagnosis.

CSF EXPLORATORY BIOMARKER STUDY FOR (DIFFERENTIAL) DIAGNOSIS OF FRONTOTEMPORAL LOBAR DEGENERATION

P1-176 CSF EXPLORATORY BIOMARKER STUDY FOR (DIFFERENTIAL) DIAGNOSIS OF FRONTOTEMPORAL LOBAR DEGENERATION Joery Goossens, Julie van der Zee, Sara Van Mossevelde, Eugeen Vanmechelen, Tobi Van den Bossche, Bart De Vil, Anne Sieben, Jean-Jacques Martin, Patrick Cras, Johan Goeman, Peter Paul de Deyn, Christine Van Broeckhoven, Sebastiaan Engelborghs, Reference Center for Biological Markers of Dementia (BIODEM), Laboratory of Neurochemistry and Behavior, Institute Born-Bunge, University of Antwerp, Antwerp, Belgium; 2 Laboratory of Neurogenetics, Institute Born-Bunge, University of Antwerp, Antwerp, Belgium; Neurodegenerative Brain Diseases Group, Department of Molecular Genetics, VIB, Antwerp, Belgium; Department of Neurology, Antwerp University Hospital, Antwerp, Belgium; 5 Department of Neurology and Memory Clinic, Hospital Network Antwerp (ZNA) Middelheim and Hoge Beuken, Antwerp, Belgium; ADx NeuroSciences, Ghent, Belgium; Laboratory of Neurobiology, Institute Born-Bunge, University of Antwerp, Antwerp, Belgium; 8 Biobank, Institute Born-Bunge, University of Antwerp, Antwerp, Belgium. Contact e-mail: joery.goossens@uantwerpen.be