Recognition of cognitive dysfunction in hospitalised older patients: a flash mob study

BACKGROUND

It is important that healthcare professionals recognise cognitive dysfunction in hospitalised older patients in order to address associated care needs, such as enhanced involvement of relatives and extra cognitive and functional support. However, studies analysing medical records suggest that healthcare professionals have low awareness of cognitive dysfunction in hospitalised older patients. In this study, we investigated the prevalence of cognitive dysfunction in hospitalised older patients, the percentage of patients in which cognitive dysfunction was recognised by healthcare professionals, and which variables were associated with recognition.

METHODS

A multicentre, nationwide, cross-sectional observational study was conducted on a single day using a flash mob study design in thirteen university and general hospitals in the Netherlands. Cognitive function was assessed in hospitalised patients aged ≥ 65 years old, who were admitted to medical and surgical wards. A Mini-Cog score of < 3 out of 5 indicated cognitive dysfunction. The attending nurses and physicians were asked whether they suspected cognitive dysfunction in their patient. Variables associated with recognition of cognitive dysfunction were assessed using multilevel and multivariable logistic regression analyses.

RESULTS

347 of 757 enrolled patients (46%) showed cognitive dysfunction. Cognitive dysfunction was recognised by attending nurses in 137 of 323 patients (42%) and by physicians in 156 patients (48%). In 135 patients (42%), cognitive dysfunction was not recognised by either the attending nurse or physician. Recognition of cognitive dysfunction was better at a lower Mini-Cog score, with the best recognition in patients with the lowest scores. Patients with a Mini-Cog score < 3 were best recognised in the geriatric department (69% by nurses and 72% by physicians).

CONCLUSION

Cognitive dysfunction is common in hospitalised older patients and is poorly recognised by healthcare professionals. This study highlights the need to improve recognition of cognitive dysfunction in hospitalised older patients, particularly in individuals with less apparent cognitive dysfunction. The high proportion of older patients with cognitive dysfunction suggests that it may be beneficial to provide care tailored to cognitive dysfunction for all hospitalised older patients.

Young-onset dementia in memory clinics in the Netherlands: Study design and description of PRECODE-GP

The disease trajectory and healthcare requirements of patients with young-onset dementia (YOD) differ from those of older patients. Accurate data about YOD is crucial to improve diagnosis and optimize care. PRECODE-GP aims to set up a prospective national database of patients with YOD to gain insight into the occurrence and characteristics of patients with YOD in memory clinics in the Netherlands. The national database includes data from dementia patients aged <70 years at diagnosis, collected by local memory clinics (MCs). Data included demographic information, clinical variables, and (etiological) diagnoses. Between July 2019 and December 2022, 781 patients with a mean age of 62±6y at diagnosis (range 37 to 69y) were included from 39 MCs. Most (n = 547,70%) were diagnosed with dementia due to Alzheimer's disease (AD). Patients with Frontotemporal lobe dementia (FTD, n = 87, 11%) were youngest (61±6.0y). Over half (55%) of patients were experiencing symptoms for ≥2 years. We initiated a Dutch national YOD database to improve diagnosis and care for this underrepresented and vulnerable patient group. The database provides a basis for future in-depth studies on YOD.

Cerebrospinal Fluid Amyloid-β Subtypes in Confirmed Frontotemporal Lobar Degeneration Cases: A Pilot Study

To investigate amyloid-β (Aβ) in frontotemporal dementia (FTD), cerebrospinal fluid (CSF) Aβ38, Aβ40, and Aβ42 in frontotemporal lobar degeneration (FTLD; N = 18 genetically and/or pathologically confirmed and N = 8 FTD with concomitant amyotrophic lateral sclerosis) were compared with Alzheimer's disease (AD; pathological or Pittsburgh-compound-B Positron-emission-tomography (PIB-PET) positive; N = 25) and controls (N = 24). For all the Aβ subtypes, group difference was seen and post-hoc analysis revealed lower levels in FTLD compared to controls (p≤0.05). Aβ42/40 ratio showed no difference between FTLD and controls; however, a difference was seen between AD versus FTLD (p < 0.01). This is an intriguing finding, suggesting a possible role of Aβ in FTLD pathogenesis.

Tau Rather than TDP-43 Proteins are Potential Cerebrospinal Fluid Biomarkers for Frontotemporal Lobar Degeneration Subtypes: A Pilot Study

BACKGROUND

Frontotemporal dementia (FTD) is a heterogeneous disease both at the clinical, genetic, and pathobiological level. The underlying pathological spectrum (termed FTLD, frontotemporal lobar degeneration) is in most cases defined by accumulation of either tau (FTLD-tau) or TDP-43 proteins (FTLD-TDP). Biomarkers to differentiate these subtypes are not yet available, whereas these are essential requirements to study the natural course of disease and for homogeneous inclusion of patients in clinical studies.

OBJECTIVE

To study if a combination of total (t-) and phosphorylated (p-)tau, and t-TDP-43 and p-TDP-43 proteins in cerebrospinal fluid (CSF) is suitable to discriminate FTLD-tau and FTLD-TDP subtypes.

METHODS

We developed immunoassays for the quantification of t-TDP-43 and p-TDP-43 proteins and used commercially available assays for the quantification of t-tau and p-tau proteins. We quantified these proteins in ventricular CSF samples from neuropathologically defined FTLD-tau and FTLD-TDP cases to study the reflection of underlying brain pathology in CSF composition, and in lumbar CSF samples from FTLD-tau and FTLD-TDP patients to study the diagnostic potential of CSF biomarkers.

RESULTS

In ventricular CSF, t-TDP-43 and t-tau levels, when combined into one model, were significantly different between neuropathologically-defined FTLD-tau and FTLD-TDP cases. In a pilot study using lumbar CSF, the p-tau/t-tau ratio, but not t-TDP-43 levels, were significantly different between FTLD-TDP and FTLD-tau patients.

CONCLUSION

We conclude that with current available methods, CSF tau, rather than TDP-43 proteins, may have diagnostic value in the differentiation of FTLD patients with either tau or TDP-43 pathology.

Clinico-Pathological Correlations of the Frontal Lobe Syndrome: Results of a Large Brain Bank Study

AIMS

A clinical frontal lobe syndrome (FLS) is generally attributed to functional or structural disturbances within frontal-subcortical circuits. We studied the distribution of pathological brain changes in FLS. Additionally, the prevalence of FLS among various disorders was studied.

METHODS

We systematically screened clinical files of donors to the Netherlands Brain Bank (n = 2,814) for FLS. A total of 262 FLS cases were identified, and the distribution of postmortem pathological changes within the frontal-subcortical circuits was extracted from their neuropathological reports.

RESULTS

In 244 out of 262 patients (93%), pathological changes within the frontal-subcortical circuits were found: 90 subjects (34%) with frontal cortical pathology and 18 (7%) with pathology restricted to subcortical grey matter nuclei, whereas 136 subjects (52%) showed both cortical and subcortical pathology. In 18 subjects (7%), no pathology was found in the examined areas. The prevalence of FLS was highest in frontal-temporal lobar degeneration, followed by progressive supranuclear palsy and vascular dementia [χ(2)(6, n = 1,561) = 222.64, p < 0.01].

CONCLUSION

In this large brain bank study, the distribution of pathological changes in subjects with FLS was shown to be frontal-subcortical for the first time. A minority of FLS cases had pathology in the subcortical regions only or no frontal pathology at all.

Discriminative and prognostic potential of cerebrospinal fluid phosphoTau/tau ratio and neurofilaments for frontotemporal dementia subtypes

Introduction

A decreased cerebrospinal fluid (CSF) p-Tau₁₈₁ to total tau ratio (p/t-tau) is a biomarker for frontotemporal lobar degeneration with TDP43 inclusions (FTLD-TDP) and for amyotrophic lateral sclerosis (ALS). CSF light chain neurofilaments (NfL) are increased in ALS. We examined whether CSF p/t-tau and NfL are related to ALS status in FTLD-TDP.

Methods

We compared CSF p/t-tau and NfL levels between patients with FTLD-TDP with ALS (n = 15), FTLD-TDP without ALS (n = 17), FTLD-Tau (n = 6), Alzheimer's disease (AD; n = 25), and subjective memory complaints (SMC, n = 24).

Results

Apart from FTLD-Tau, all groups differed significantly with increasing p/t-tau ratios from FTLD-TDP with ALS to FTLD-TDP without ALS to AD and SMC. CSF NfL was very high in FTLD-TDP with ALS followed by FTLD-TDP without ALS, AD, and SMC. Both biomarkers correlated with survival.

Discussion

CSF p/t-tau ratio and NfL levels are strongly driven by ALS status. These markers, therefore, appear to be more of prognostic than diagnostic significance.

Immunohistochemical characterization of novel monoclonal antibodies against the N-terminus of amyloid β-peptide

Abstract Amyloid β-peptide (Aβ) is a key molecule in Alzheimer's disease (AD). Reliable immunohistochemical (IHC) methods to detect Aβ and Aβ-associated factors (AAF) in brain specimens are needed to determine their role in AD pathophysiology. Formic acid (FA) pre-treatment, which is generally used to enable efficient detection of Aβ with IHC, induces structural modifications within the Aβ, as well as in AAF. Consequently, interpretation of double IHC stainings becomes difficult. Therefore, serial stainings of two newly produced monoclonal antibodies (mAbs) VU-17 and IC16 and two other mAbs (6E10 and 3D6) were performed with four different pre-treatments (no pre-treatment, Tris/EDTA, citrate and FA) and additionally six IHC characteristics were scored: diffuse/compact/classic plaques, arteries with cerebral Aβ angiopathy, dyshoric angiopathy, capillaries with dyshoric angiopathy. Subsequently, these stainings were compared with IHC procedures, which are frequently used in a diagnostic setting, employing mAbs 4G8 and 6F/3D with FA pre-treatment. IHC Aβ patterns obtained with VU-17 and, IC16 and 3D6 without the use of FA pre-treatment were comparable to those obtained with 4G8 and 6F/3D upon FA pre-treatment. Omission of FA pre-treatment gives the advantage to allow double IHC stainings, detecting both Aβ and AAF that otherwise would have been structural modificated upon FA pre-treatment.

Microbleeds relate to altered amyloid-β metabolism in Alzheimer's disease

Cerebral microbleeds (MBs) may relate to amyloid in dementia. We selected 26 probable Alzheimer's disease (AD) patients with MBs, 26 age- and sex-matched AD patients without MBs, 11 vascular dementia (VaD) patients, and 22 patients with subjective complaints. We measured amyloid beta 1-42 (Aβ42) and 1-40 (Aβ40) in cerebrospinal fluid (CSF) and plasma, and blood-brain barrier (BBB) function using albumin ratios. CSF Aβ42 was lowest in AD with MBs, whereas Aβ40 was selectively decreased in VaD. In plasma, amyloid-beta was nonsignificantly elevated in VaD compared with controls. Higher albumin ratios in VaD suggested blood-brain barrier dysfunction. A MB pattern suggestive of cerebral amyloid angiopathy (CAA) related to lower CSF Aβ42, while a non-cerebral amyloid angiopathy specific MB distribution related to higher plasma Aβ40. Amyloid-beta is differentially implicated in AD with MBs and VaD. MB distribution related to different amyloid profiles, supporting distinct etiologies. Our results suggest that Aβ42 is retained in cerebrovasculature of AD patients with MBs, while in contrast, VaD patients may possibly drain amyloid.

New research criteria for the diagnosis of Alzheimer's disease applied in a memory clinic population

BACKGROUND

In the newly proposed research criteria for Alzheimer's disease (AD), patients are defined as having memory dysfunction in addition to either hippocampal atrophy or an abnormal cerebrospinal fluid (CSF) profile. This study applies the criteria in a memory clinic population, using clinical criteria as the reference criterion.

METHODS

138 AD patients, 145 nondemented subjects, 78 patients with other dementias and 91 patients with mild cognitive impairment (MCI) were included. Dichotomized medial temporal lobe atrophy (MTA) score on MRI and dichotomized CSF profiles (based on beta-amyloid1-42, tau and phosphorylated tau at threonine 181 levels) were used in combination with an episodic memory test to assess sensitivity, specificity and likelihood ratios (LR) of the newly proposed criteria and their components separately.

RESULTS

We found specificities of 95 and 49% for comparison with nondemented subjects and other demented patients, respectively, with a sensitivity of 86% for AD. Specificity was highest (100 and 77%, respectively, LR+ = 48) when both MTA score and CSF profile were abnormal in addition to the episodic memory test, at the cost of a low sensitivity (48%).

CONCLUSION

The newly proposed research criteria for AD yield a good specificity for comparison with nondemented subjects. When the type of dementia is clinically doubted, however, at least two supportive features should be considered (i.e. abnormal MTA score and CSF profile) in addition to memory impairment as core diagnostic criterion.

Batch prepared protein standards for cerebrospinal fluid (CSF) biomarkers for neurodegeneration

Immuno-assays are increasingly used for quantification of protein biomarkers for neurodegeneration. It has been proposed to use such cerebrospinal fluid (CSF) protein biomarkers as diagnostic tests for Alzheimer's disease. In two recent world-wide validation studies we found the analytical accuracy to be poor (inter-laboratory coefficient of variation, CV>10%) for CSF tau protein, CSF phospho-tau protein, CSF amyloid beta protein and the CSF neurofilament light chain protein. Retrospectively we suspected that the lack of preparation of accurate and consistent protein standards may have been one reason for the poor inter-laboratory CV. Here we confirm this hypothesis prospectively under standardised and optimised conditions. The CVs for CSF tau, CSF phospho-tau and CSF amyloid beta of individually prepared standards are 8%, 12% and 12% compared to significantly lower CVs for batch prepared standards (5%, 8%, 7%, respectively, p<0.05). This issue will need to be solved in order to ensure that the attempts to include these CSF protein biomarkers either as a diagnostic tool or a secondary outcome measure for treatment trials will be successful.

Additional value of CSF amyloid-beta 40 levels in the differentiation between FTLD and control subjects

To determine the additional value of cerebrospinal fluid (CSF)amyloid-beta1-40 (Abeta40) next to amyloid-beta1-42 (beta42), total tau (Tau), and tau phosphorylated at threonine-181 (pTau) to distinguish patients with frontotemporal lobar degeneration (FTLD), Alzheimer's disease (AD), and controls, we measured CSF levels of Abeta40, Abeta42, pTau, and Tau in 55 patients with FTLD, 60 with AD, and 40 control subjects. Logistic regression was used to identify biomarkers that best distinguished the groups. Additionally, a decision tree (cost=test method; Matlab 7.7) was used to predict diagnosis selecting the best set of biomarkers with the optimal cut-off. Logistic regression showed that Abeta42 and pTau CSF levels provided optimal distinction between AD and FTLD. A combination of Abeta42, Tau, and Abeta40 optimally discriminated FTLD from controls and AD from controls. The decision tree used Abeta42 (cut-off 578 pg/ml) to identify AD (positive predictive value (PPV) 97%), followed by Tau(cut-off 336 pg/ml) to identify FTLD (PPV 67%), and in the last step,Abeta40 (cut-off 10 ng/ml) was used to differentiate controls (PPV68%). Applying CSF Abeta40 levels in the model, the PPV of diagnosis increased to 75% as opposed to 70% when only Abeta42 and Tau were used. CSF Abeta40 levels added to the conventional CSF biomarkers increases the potential to discriminate subjects with dementia from controls. Our findings favor the implementation of CSF Abeta40 in differential diagnosis between FTLD, AD, and control subjects.

Amyloid-β(1–42), Total Tau, and Phosphorylated Tau as Cerebrospinal Fluid Biomarkers for the Diagnosis of Alzheimer Disease

Background: To improve ante mortem diagnostic accuracy of Alzheimer disease (AD), measurement of the biomarkers amyloid-β(1–42) (Aβ42), total tau (Tau), and tau phosphorylated at threonine181 (pTau) in cerebrospinal fluid (CSF) has been proposed. We have used these markers and evaluated their performance.

Methods: From January 2001 to January 2007, we assessed Aβ42, Tau, and pTau by commercial ELISAs in CSF from 248 consecutive AD patients and 131 patients with subjective memory complaints attending our outpatient memory clinic. Diagnoses were made blind to the results of the biomarker assays. We assessed sensitivity and specificity and analyzed trends over time.

Results: Interassay CVs from analysis of pools of surplus CSF specimens were mean 11.3% (SD 4.9%) for Aβ42; 9.3% (1.5%) for Tau, and 9.4% (2.5%) for pTau, respectively (n = 7–18). To achieve 85% sensitivity, cutoff values were 550 (95% CI 531–570) ng/L for Aβ42; 375 (325–405) ng/L for Tau, and 52 (48–56) ng/L for pTau. Corresponding specificities were 83% (95% CI 76%–89%) for Aβ42, 78% (70%–85%) for Tau, and 68% (60%–77%) for pTau. Logistic regression to investigate the simultaneous impact of the 3 CSF biomarkers on the diagnosis yielded a sensitivity of 93.5% and specificity of 82.7%, at a discrimination line of Aβ42 = 373 + 0.82 × Tau. The area under the ROC curves of Tau and pTau showed significant fluctuation over time.

Conclusions: CSF biomarkers Aβ42 and Tau can be used as a diagnostic aid in AD. pTau did not have additional value over these 2 markers. Cutoff values, sensitivities, specificities, and discrimination lines depend on the patient groups studied and laboratory experience.

Baseline CSF p-tau levels independently predict progression of hippocampal atrophy in Alzheimer disease

OBJECTIVE

To investigate whether baseline CSF biomarkers are associated with hippocampal atrophy rate as a measure of disease progression in patients with Alzheimer disease (AD), patients with mild cognitive impairment (MCI), and controls, controlling for baseline neuropsychological and MRI findings.

METHODS

We assessed data from 31 patients with AD, 25 patients with MCI, and 19 controls (mean age 68 +/- 8 years; 39 [52%] female) who visited our memory clinic and had received serial MRI scanning (scan interval 1.7 +/- 0.7 years). At baseline, CSF biomarkers (amyloid beta 1-42, tau, and tau phosphorylated at threonine 181 [p-tau]) were obtained, as well as neuropsychological data. Baseline MRI scans were assessed using visual rating scales for medial temporal lobe atrophy (MTA), global cortical atrophy, and white matter hyperintensities. Hippocampal atrophy rates were estimated using regional nonlinear "fluid" registration of follow-up scan to baseline scan.

RESULTS

Stepwise multiple linear regression, adjusted for age and sex, showed that increased CSF p-tau levels (beta [standard error]: -0.79 [0.35]) at baseline was independently associated with higher subsequent hippocampal atrophy rates (p < 0.05), together with poorer memory performance (0.09 [0.04]) and more severe MTA (-0.60 [0.21]). The association of memory function with hippocampal atrophy rate was explained by the link with diagnosis, because it disappeared from the model after we additionally corrected for diagnosis.

CONCLUSIONS

Baseline CSF levels of tau phosphorylated at threonine 181 are independently associated with subsequent disease progression, as reflected by hippocampal atrophy rate. This effect is independent of baseline neuropsychological and MRI predictors. Our results imply that predicting disease progression can best be achieved by combining information from different modalities.

CSF biomarkers in relationship to cognitive profiles in Alzheimer disease

OBJECTIVE

To investigate the relationship between CSF biomarkers and cognitive profiles in Alzheimer disease (AD).

METHODS

We included 177 patients with AD. Digit Span, Visual Association Test (VAT), VAT object naming, Trail Making Test (TMT), and category fluency were used to assess cognitive functions. Disease severity was assessed using Mini-Mental State Examination; functional impairment was rated by Clinical Dementia Rating. In CSF, levels of amyloid-beta 1-42 (Abeta(1-42)), tau, and tau phosphorylated at threonine 181 (p-tau) were measured. K-means cluster analysis was performed with the three biomarkers to obtain three clusters. Multivariate analysis of variance for repeated measures was performed with CSF cluster as between-subjects factor, neuropsychological z scores as within-subjects variable, and age, sex, and education as covariates.

RESULTS

Cluster 1 consisted of 88 patients (49%) with relatively high levels of Abeta(1-42) and low levels of tau and p-tau. Cluster 2 contained 72 patients (41%) with relatively low levels of Abeta(1-42) and high levels of tau and p-tau. Cluster 3 was made up of 17 patients (10%) with low levels of Abeta(1-42) and very high levels of tau and p-tau. No differences between clusters on age, sex, education, APOE genotype, disease duration, functional impairment, or disease severity were found. Patients in cluster 3 performed worse on VAT, TMT-A and -B, and fluency.

CONCLUSIONS

Clusters of CSF biomarker levels are related to cognitive profiles in Alzheimer disease. A subgroup of patients with extremely high CSF levels of tau and tau phosphorylated at threonine 181 shows a distinct cognitive profile with more severe impairment of memory, mental speed, and executive functions, which cannot be explained by disease severity.

Relationship of cerebrospinal fluid markers to 11C-PiB and 18F-FDDNP binding

The purpose of this study was to investigate the potential relationships between cerebrospinal fluid (CSF) measurements of beta-amyloid-1-42 (Abeta(1-42)) and total tau to (11)C-Pittsburgh compound B ((11)C-PiB) and 2-(1-{6-[(2-(18)F-fluoroethyl)(methyl)amino]-2-naphthyl}ethylidene) malononitrile ((18)F-FDDNP) binding as measured using PET.

METHODS

A total of 37 subjects were included, consisting of 15 patients with Alzheimer disease (AD), 12 patients with mild cognitive impairment, and 10 healthy controls. All subjects underwent a lumbar puncture and PET using both (11)C-PiB and (18)F-FDDNP. For both PET tracers, parametric images of binding potential were generated. Potential associations of CSF levels of Abeta(1-42) and tau with (11)C-PiB and (18)F-FDDNP binding were assessed using Pearson correlation coefficients and linear regression analyses.

RESULTS

For both global (11)C-PiB and (18)F-FDDNP binding, significant correlations with CSF levels of Abeta(1-42) (r = -0.72 and -0.37, respectively) and tau (r = 0.58 and 0.56, respectively) were found across groups (all P < 0.001, except P < 0.05 for correlation between (18)F-FDDNP and Abeta(1-42)). Linear regression analyses showed that, adjusted for regional volume, age, sex, and diagnosis, global (11)C-PiB uptake had an inverse association with Abeta(1-42) CSF levels (standardized beta = -0.50, P < 0.001), whereas there was a positive association between global (18)F-FDDNP binding and tau CSF levels (standardized beta = 0.62, P < 0.01).

CONCLUSION

The good agreement between these 2 different types of biomarkers (i.e., CSF and PET) provides converging evidence for their validity. The inverse association between (11)C-PiB and CSF tau Abeta(1-42) confirms that (11)C-PiB measures amyloid load in the brain. The positive association between (18)F-FDDNP and CSF tau suggests that at least part of the specific signal of (18)F-FDDNP in AD patients is due to tangle formation.

Quantification of amyloid-beta 40 in cerebrospinal fluid

BACKGROUND

Truncated forms and full-length forms of the amyloid-beta 40 (Abeta40) are key molecules in the pathogenesis of dementia, and are detectable in CSF. Reliable methods to detect these biomarkers in CSF are of great importance for understanding the disease mechanisms and for diagnostic purposes.

METHODS

VU-alpha-Abeta40, a monoclonal antibody (mAb) specifically detecting Abeta40, was generated and characterized by solid and fluid phase ELISA, surface plasmon resonance spectroscopy (SPRS), immunoprecipitation (IP), immunohistochemical and Western blot (WB) analysis. In addition, an ELISA with VU-alpha-Abeta40 as catching and 6E10 as detecting mAbs was set up and validated. This ELISA was used to measure Abeta40 in CSF of controls (N=27), patients with Alzheimer's disease (AD; N=20), frontotemporal lobe dementia (FTLD; N=14), noninflammatory (N=15) and inflammatory (N=15) neurological conditions.

RESULTS

VU-alpha-Abeta40 specifically recognizes Abeta40 with high affinity (K(A)=1.3x10(9) M(-1)) and detects Abeta40 in AD brain specimens. The developed sandwich ELISA has a detection limit of 0.21 ng/mL, a mean recovery of 90%, and an intra- and inter-assay CV of 1.4% and 7.3%. FTLD patients had a lower mean level of Abeta40 (8.8 (1.9) ng/mL) than controls (12.0 (1.7) ng/mL); p<0.01).

CONCLUSIONS

VU-alpha-Abeta40 was successfully implemented in an ELISA which enables us to measure Abeta40 accurately in human CSF. Clinical validation revealed lower levels of Abeta40 in FTLD patients. This finding opens new possibilities for early and differential diagnosis of dementia.

A worldwide multicentre comparison of assays for cerebrospinal fluid biomarkers in Alzheimer's disease

BACKGROUND

Different cerebrospinal fluid (CSF) amyloid-beta 1-42 (Abeta(1-42)), total Tau (Tau) and Tau phosphorylated at threonine 181 (P-Tau) levels are reported, but currently there is a lack of quality control programmes. The aim of this study was to compare the measurements of these CSF biomarkers, between and within centres.

METHODS

Three CSF-pool samples were distributed to 13 laboratories in 2004 and the same samples were again distributed to 18 laboratories in 2008. In 2004 six laboratories measured Abeta(1-42), Tau and P-Tau and seven laboratories measured one or two of these marker(s) by enzyme-linked immunosorbent assays (ELISAs). In 2008, 12 laboratories measured all three markers, three laboratories measured one or two marker(s) by ELISAs and three laboratories measured the markers by Luminex.

RESULTS

In 2004, the ELISA intercentre coefficients of variance (interCV) were 31%, 21% and 13% for Abeta(1-42), Tau and P-Tau, respectively. These were 37%, 16% and 15%, respectively, in 2008. When we restricted the analysis to the Innotest (N = 13) for Abeta(1-42), lower interCV were calculated (22%). The centres that participated in both years (N = 9) showed interCVs of 21%, 15% and 9% and intra-centre coefficients (intraCV) of variance of 25%,18% and 7% in 2008.

CONCLUSIONS

The highest variability was found for Abeta(1-42). The variabilities for Tau and P-Tau were lower in both years. The centres that participated in both years showed a high intraCV comparable to their interCV, indicating that there is not only a high variation between but also within centres. Besides a uniform standardization of (pre)analytical procedures, the same assay should be used to decrease the inter/intracentre variation.

Serum amyloid p component as a biomarker in mild cognitive impairment and Alzheimer's disease

BACKGROUND

Serum amyloid P component (SAP), present in amyloid-beta (Abeta) plaques in Alzheimer's disease (AD), may protect Abeta deposits against proteolysis, thereby promoting plaque formation. The aim was to investigate if SAP levels in cerebrospinal fluid (CSF) and serum can be used to discriminate controls, AD and mild cognitive impairment (MCI) patients, and to identify incipient AD among MCI patients.

METHODS

SAP levels in CSF and serum were determined in 30 controls, 67 MCI and 144 AD patients. At follow-up, 39 MCI patients had progressed to dementia, while 25 had remained stable (mean follow-up time: 2.6 +/- 1.0 and 2.1 +/- 0.8 years).

RESULTS

Cross-sectionally no differences were found in SAP levels in CSF and serum between the groups. MCI patients that had progressed to dementia at follow-up had lower CSF SAP levels (13 microgram/l, range 3.3-199.3 microgram/l) than MCI nonprogressors (20.2 microgram/l, range 7.0-127.7 microgram/l; p < 0.05) [corrected]. A low CSF SAP level was associated with a 2-fold increased risk of progression to AD (hazard ratio = 2.2; 95% confidence interval = 0.9-5.4).

CONCLUSION

Our data suggest that measurement of CSF SAP levels can aid in the identification of incipient AD among MCI patients.

Variability in longitudinal cerebrospinal fluid tau and phosphorylated tau measurements

BACKGROUND

The influence of assay variation and duration of storage on changes in cerebrospinal fluid (CSF) levels of tau and phosphorylated (P)-tau with time was evaluated in 112 patients with various neurological disorders.

METHODS

These patients (aged 66+/-9 years, 52% male), referred to our memory clinic, underwent two spinal taps (mean interval 19 months) and the baseline samples were assayed twice in a sandwich enzyme-linked immunosorbent assay (ELISA): once after the first spinal tap (A1) and once in a separately stored aliquot (A2) simultaneous with the follow-up sample (B).

RESULTS

Coefficients of variances (CVs) of tau and P-tau levels determined in repeated spinal taps (DeltaB-A2) measured in one assay (10.9% and 7.6%) were lower (p<0.01) than the CVs observed in two different (DeltaB-A1) assays (16.5% and 11.7%). The CVs of tau and P-tau measurement of one CSF sample repeated on two occasions (DeltaA1-A2) were 12.3% and 8.6%. A difference in mean P-tau level was found if the same CSF samples were repeatedly measured in two different ELISAs (A1-A2).

CONCLUSIONS

Longitudinal CSF tau and P-tau are best measured in one assay resulting in a lower variability compared to measurement in two different assays. The within person variability in levels of these markers currently limits the use of these ELISAs in a longitudinal clinical setting.

CSF biomarker levels in early and late onset Alzheimer's disease

OBJECTIVE

To compare CSF levels of beta-amyloid 1-42 (Abeta(1-42)), total tau (tau) and tau phosphorylated at threonine 181 (ptau-181) between AD patients and controls according to age.

METHODS

248 AD patients (48% men) and 127 controls (51% men, 22 volunteers and 105 subjective complainers) underwent lumbar puncture. Both patients and controls were divided into a young (<65 years) and old (>or=65 years) group.

RESULTS

All three biomarkers showed main effects of diagnosis (p<0.001). There was an interaction between diagnosis and age for all three biomarkers (p<0.05), as old controls had lower Abeta(1-42) and higher (p)tau than young controls (Abeta(1-42) 699+/-250 versus 866+/-191pg/ml, tau 408+/-245 versus 243+/-102pg/ml, ptau-181 60+/-28 versus 42+/-15pg/ml), but there was no difference according to age among AD patients (Abeta(1-42) 451+/-178 versus 425+/-146pg/ml, tau 741+/-460 versus 798+/-467pg/ml, ptau-181 91+/-42 versus 91+/-41pg/ml).

CONCLUSION

We found that the older control group had lower Abeta(1-42) and higher (p)tau compared to the younger control group. This suggests that older individuals may have AD pathology, even in the absence of objective cognitive impairment.

Assessment of cognition in Parkinson's disease

OBJECTIVE

To develop a short, practical instrument that is sensitive to the specific cognitive deficits in Parkinson's disease (PD) for comparing groups in research situations and for assessing change in cognitive functioning over time.

METHODS

A literature search was conducted to identify the most frequently affected cognitive domains in PD and to select candidate items for the initial scale. This scale was tested in 85 patients and 75 age-, education-, and sex-matched control subjects. Items that met predefined criteria for data quality, reproducibility, and discriminative properties were included in the final scale.

RESULTS

The final scale, the SCOPA-COG (SCales for Outcomes of PArkinson's disease-cognition), consists of 10 items with a maximum score of 43, with higher scores reflecting better performance. The test-retest reliability of the total score was 0.78 (intraclass correlation coefficient) and ranged from 0.40 to 0.75 for individual items (weighted kappa). Cronbach's alpha was 0.83. Construct validity of the scale was supported by the expected correlations with the CAMCOG (Cambridge Cognitive Examination) and the Mini-Mental State Examination (MMSE) and by differences found between groups of participants classified by dementia status and between patients grouped by disease severity. The scale showed a clear trend toward lower cognition scores for patients with more advanced PD. The coefficient of variation of the SCOPA-COG was higher than that of the CAMCOG or the MMSE, indicating a better ability to detect differences between individuals.

CONCLUSION

The SCOPA-COG is a short, reliable, and valid instrument that is sensitive to the specific cognitive deficits in PD.