Femke H. Bouwman

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-beta(1-42) (Abeta42), total tau (Tau), and tau phosphorylated at threonine(181) (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 Abeta42, 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 Abeta42; 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 Abeta42; 375 (325-405) ng/L for Tau, and 52 (48-56) ng/L for pTau. Corresponding specificities were 83% (95% CI 76%-89%) for Abeta42, 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 Abeta42 = 373 + 0.82 x Tau. The area under the ROC curves of Tau and pTau showed significant fluctuation over time. CONCLUSIONS CSF biomarkers Abeta42 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.

Optimizing Patient Care and Research: The Amsterdam Dementia Cohort

Since its opening in 2000, patient care and research go hand in hand at the Alzheimer center of the VU University Medical Center, both organized in such a way that they mutually strengthen each other. Our mission is to give patients a voice by lifting the stigma on dementia, to find new diagnostic and treatment strategies, and, ultimately, to cure diseases that cause dementia. Our healthcare pathway is uniquely designed to accommodate all necessary investigations for the diagnostic work-up of dementia in one day (one-stop shop). A second unique feature is that research has been fully integrated in the healthcare pathway. The resulting Amsterdam Dementia Cohort now includes over 4000 patients, and for the majority of these, we have MRI, EEG, blood (serum, plasma), DNA, and CSF available. The Amsterdam Dementia Cohort forms the basis of much of our research, which focuses on four major research lines: 1) variability in manifestation, 2) early diagnosis, 3) vascular factors, and 4) interventions. By answering research questions closely related to clinical practice, the results of our research can be looped back to improve clinical work-up for our patients.

The cerebrospinal fluid "Alzheimer profile": Easily said, but what does it mean?

We aimed to identify the most useful definition of the “cerebrospinal fluid Alzheimer profile,” based on amyloid‐ß1‐42 (Aβ42), total tau, and phosphorylated tau (p‐tau), for diagnosis and prognosis of Alzheimers disease (AD).

Multicenter assessment of CSF- phosphorylated tau for the prediction of conversion of MCI

Background: The measurement of hyperphosphorylated tau (p-tau) in CSF has been proposed as a biomarker candidate for the prediction of Alzheimer disease (AD) in patients with mild cognitive impairment (MCI). However, a standard quantitative criterion of p-tau has not been evaluated. Objective: To assess in a multicenter study the predictive accuracy of an a priori defined criterion of tau phosphorylated at threonine 231 (p-tau231) for the prediction of conversion from MCI to AD during a short-term observation interval. Methods: The study included 43 MCI converters, 45 stable MCI (average follow-up interval = 1.5 years), and 57 healthy controls (at baseline only). Subjects were recruited at four international expert sites in a retrospective study design. Cox regression models stratified according to center were used to predict conversion status. Bootstrapped 95% CIs of classification accuracy were computed. Results: Levels of p-tau231 were a significant predictor of conversion (B = 0.026, p = 0.001), independent of age, gender, Mini-Mental State Examination, and ApoE genotype. For an a priori–defined cutoff point (27.32 pg/mL), sensitivity ranged between 66.7 and 100% and specificity between 66.7 and 77.8% among centers. The bootstrapped mean percentage of correctly classified cases was 79.95% (95% CI = 79.9 to 80.00%). Post hoc defined cutoff values yielded a mean bootstrapped classification accuracy of 80.45% (95% CI = 80.24 to 80.76%). Conclusions: An a priori defined cutoff value of p-tau231 yields relatively stable results across centers, suggesting a good feasibility of a standard criterion of p-tau231 for the prediction of Alzheimer disease.

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.

CSF and MRI markers independently contribute to the diagnosis of Alzheimer's disease

BACKGROUND Decreased amyloid beta (1-42) (Abeta42) and increased (phosphorylated) tau in cerebrospinal fluid (CSF) are considered to be a reflection of plaques, tangles, and neuronal degeneration in Alzheimers disease (AD). Atrophy of the medial temporal lobe (MTA) on magnetic resonance imaging (MRI) reflects neuronal loss in this area. OBJECTIVE To compare diagnostic accuracy of CSF biomarkers and MTA in AD versus controls. METHODS Abeta42, tau and tau phosphorylated at threonine 181 (Ptau-181) were measured in CSF from 61 AD patients and 32 controls by sandwich enzyme-linked immunosorbent assay. A CSF biomarker profile for AD was constructed. MTA was rated visually on MRI. RESULTS When AD patients and controls were evaluated separately, no correlations were present between the CSF markers and MTA score. Both MTA and CSF biomarker profile were independently associated with the diagnosis AD (MTA: OR (95% CI)=28 (3-239); CSF biomarker profile: OR (95% CI)=57 (13-262)). Among individuals younger than 65 years old and without MTA 60% suffered AD, and the finding of an abnormal CSF biomarker profile was limited to AD patients only. CONCLUSIONS MTA and CSF biomarkers seem to be of incremental value for the diagnosis AD. CSF analysis is most sensitive in the absence of MTA, and especially among early-onset AD patients.

Whole-brain atrophy rate and CSF biomarker levels in MCI and AD: A longitudinal study

OBJECTIVES To assess associations between cerebrospinal fluid (CSF) biomarker levels and MRI-based whole-brain atrophy rate in mild cognitive impairment (MCI) and Alzheimers disease (AD). METHODS We included 99 patients (47 AD, 29 MCI, 23 controls) who underwent lumbar puncture at baseline and repeat MRI. A subgroup of 48 patients underwent a second lumbar puncture. CSF levels of beta-amyloid(1-42) (A beta(1-42)), tau and tau phosphorylated at threonine-181 (P-tau(181)), and whole-brain atrophy rate were measured. RESULTS Across groups, baseline A beta(1-42) and tau were modestly associated with whole-brain atrophy rate. Adjusted for age, sex and diagnosis, we found no association between A beta(1-42) or tau, and whole-brain atrophy rate. By contrast, high CSF levels of P-tau(181) showed a mild association with a lower whole-brain atrophy rate in AD but not in controls or MCI patients. Finally, whole-brain atrophy rate was associated with change in MMSE, but change in CSF biomarker levels was not. CONCLUSIONS Whole-brain atrophy rate and CSF levels of A beta(1-42,) tau or P-tau(181) provide complementary information in patients with MCI and AD.

Associations Between Cerebral Small-Vessel Disease and Alzheimer Disease Pathology as Measured by Cerebrospinal Fluid Biomarkers

IMPORTANCE It remains unclear if and how associations between cerebral small-vessel disease and Alzheimer disease (AD) pathology lead to cognitive decline and dementia. OBJECTIVE To determine associations between small-vessel disease and AD pathology. DESIGN, SETTING, AND PARTICIPANTS Cross-sectional study from January 2002 to December 2012 using the memory clinic-based Amsterdam Dementia Cohort. The study included 914 consecutive patients with available cerebrospinal fluid (CSF) and magnetic resonance imaging; 547 were patients diagnosed as having AD (54% female, mean [SD], 67 [8]; Mini-Mental State Examination score, mean [SD], 21 [5]), 30 were patients diagnosed as having vascular dementia (37% female, mean [SD], 76 [9]; Mini-Mental State Examination score, mean [SD], 24 [4]), and 337 were control participants with subjective memory complaints (42% female, mean [SD], 59 [59]; Mini-Mental State Examination score, mean [SD], 28 [2]). Linear regressions were performed with CSF biomarkers (log transformed) as dependent variables and magnetic resonance imaging measures (dichotomized) as independent, adjusted for sex, age, mediotemporal lobe atrophy, and diagnosis. An interaction term for diagnosis by magnetic resonance imaging measures was used for estimates per diagnostic group. MAIN OUTCOMES AND MEASURES We examined the associations of magnetic resonance imaging white matter hyperintensities (WMH), lacunes, microbleeds with CSF β-amyloid 42 (Aβ42), total tau, and tau phosphorylated at threonine 181 (P-tau181) as well as for a subset of apolipoprotein E (APOE) ε4 carriers and noncarriers. RESULTS Microbleed presence was associated with lower CSF Aβ42 in AD and vascular dementia (standardized beta = -0.09, P = .003; standardized beta = -0.30, P = .01), and higher CSF tau in controls (standardized beta = 0.10, P = .03). There were no effects for P-tau181. The presence of WMH was associated with lower Aβ42 in control participants and patients with vascular dementia (standardized beta = -0.18, P = .002; standardized beta = -0.32, P = .02) but not in patients with AD. There were no effects for tau or P-tau181. The presence of lacunes was associated with higher Aβ42 in vascular dementia (standardized beta = 0.17, P = .07) and lower tau in AD (standardized beta = -0.07, P = .05) but there were no effects for Aβ42 or P-tau181. Stratification for apolipoprotein E genotype revealed that these effects were mostly attributable to ε4 carriers. CONCLUSIONS AND RELEVANCE Deposition of amyloid appears aggravated in patients with cerebral small-vessel disease, especially in apolipoprotein E ε4 carriers, providing evidence for pathophysiological synergy between these 3 biological factors.

Concordance between cerebrospinal fluid biomarkers and [11C]PIB PET in a memory clinic cohort.

BACKGROUND Two approaches are available for measuring Alzheimers disease (AD) pathology in vivo. Biomarkers in cerebrospinal fluid (CSF) include amyloid-β1-42 (Aβ42) and tau. Furthermore, amyloid deposition can be visualized using positron emission tomography (PET) and [11C]Pittsburgh compound-B ([11C]PIB). OBJECTIVE We investigated concordance between CSF biomarkers and [11C]PIB PET as markers for AD pathology in a memory clinic cohort. METHODS We included 64 AD patients, 34 non-AD dementia patients, 22 patients with mild cognitive impairment (MCI), and 16 controls. [11C]PIB scans were visually rated as positive or negative. CSF biomarkers were considered abnormal based on Aβ42 alone (<550 ng/L), a more lenient Aβ42 cut-off (<640 ng/L) or a combination of both Aβ42 and tau ((373 + 0.82 tau)/Aβ42 > 1). Concordance between CSF biomarkers and [11C]PIB PET was determined. RESULTS Overall, concordance between [11C]PIB PET and CSF Aβ42 (<550 ng/L) was 84%. In discordant cases, [11C]PIB PET was more often AD-positive than Aβ42. When a more lenient Aβ42 cut-point (<640 ng/L) or a combination of Aβ42 and tau was used, concordance with [11C]PIB PET appeared to be even higher (90% and 89%). This difference is explained by a subgroup of mostly MCI and AD patients with Aβ42 levels just above cut-off. Now, in discordant cases, CSF was more often AD-positive than [11C]PIB PET. CONCLUSION Concordance between CSF Aβ42 and [11C]PIB PET was good in all diagnostic groups. Discordance was mostly seen in MCI and AD patients close to the cut-point. These results provide convergent validity for the use of both types of biomarkers as measures of AD pathology.

Apolipoprotein E Genotype Influences Presence and Severity of Delusions and Aggressive Behavior in Alzheimer Disease

Aim: We investigated differences in the prevalence and severity of 10 neuropsychiatric and behavioral symptoms according to apolipoprotein E (APOE) genotype and dementia severity in Alzheimer disease (AD). Methods: Neuropsychiatric and behavioral symptoms of 110 AD patients were assessed using the Neuropsychatric Inventory. Dementia severity was assessed using the Mini Mental State Examination (MMSE). Results: There were 27 APOE-Ε4-negative patients, 65 heterozygous patients and 18 homozygous patients. There was a significant association between the number of APOE Ε4 alleles and prevalence and severity of neuropsychiatric and behavioral symptoms that was mainly attributable to delusions and agitation/aggression, which were more common and severer among homozygous APOE Ε4 carriers. In addition, the presence of hallucinations, anxiety, apathy and aberrant motor behavior increased with deteriorating MMSE score, independently of APOE Ε4 status. Conclusions: The present study showed that the APOE Ε4 genotype modifies neuropsychiatric and behavioral phenotype in AD. In particular, it was shown that delusions and agitation/aggression were more common and severer among homozygous APOE Ε4 carriers than among heterozygous or APOE-Ε4-negative patients.