| 1. |
- Andreasen, Niels, et al.
(författare)
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Cerebrospinal fluid levels of total-tau, phospho-tau and A beta 42 predicts development of Alzheimer's disease in patients with mild cognitive impairment.
- 2003
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Ingår i: Acta neurologica Scandinavica. Supplementum. - : Hindawi Limited. - 0065-1427 .- 0001-6314. ; 179, s. 47-51
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Tidskriftsartikel (refereegranskat)abstract
- Cerebrospinal fluid (CSF) biochemical diagnostic markers may be valuable to help in the diagnosis early in the course of Alzheimer's disease (AD), especially in the phase before clinically overt dementia, i.e. in patients with mild cognitive impairment (MCI). We studied 44 patients with MCI who, at 1-year follow-up investigation, had progressed to AD with dementia, and 32 controls. Three CSF biomarkers related to the central pathogenic processes in AD were analysed, including CSF total-tau (T-tau) (as a marker for neuronal degeneration), CSF phospho-tau (P-tau) (as a marker for hyperphosphorylation of tau and possibly for the formation of neurofibrillary tangles), and CSF A beta 42 (as a marker for A beta metabolism, and possibly for the formation of senile plaques). At baseline, 35/44 (79.5%) of the MCI patients had high CSF T-tau, 31/44 (70.4%) high CSF P-tau, while 34/44 (77.3%) had low CSF-A beta 42 levels. The positive likelihood ratio was 8.45 for CSF T-tau, 7.49 for CSF P-tau and 8.20 for CSF A beta 42. These findings suggest that these CSF-markers are abnormal before the onset of clinical dementia, and that they may help to identify MCI patients that will progress to AD. CSF diagnostic markers will be especially important when drugs with potential effects on the progression of AD (e.g. gamma-secretase inhibitors) will reach the clinical phase.
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| 2. |
- Bjerke, Maria, 1977, et al.
(författare)
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Assessing the commutability of reference material formats for the harmonization of amyloid beta measurements.
- 2016
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Ingår i: Clinical chemistry and laboratory medicine : CCLM / FESCC. - : Walter de Gruyter GmbH. - 1437-4331 .- 1434-6621. ; 54:7, s. 1177-91
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The cerebrospinal fluid (CSF) amyloid-β (Aβ42) peptide is an important biomarker for Alzheimer's disease (AD). Variability in measured Aβ42 concentrations at different laboratories may be overcome by standardization and establishing traceability to a reference system. Candidate certified reference materials (CRMs) are validated herein for this purpose. METHODS: Commutability of 16 candidate CRM formats was assessed across five CSF Aβ42 immunoassays and one mass spectrometry (MS) method in a set of 48 individual clinical CSF samples. Promising candidate CRM formats (neat CSF and CSF spiked with Aβ42) were identified and subjected to validation across eight (Elecsys, EUROIMMUN, IBL, INNO-BIA AlzBio3, INNOTEST, MSD, Simoa, and Saladax) immunoassays and the MS method in 32 individual CSF samples. Commutability was evaluated by Passing-Bablok regression and the candidate CRM termed commutable when found within the prediction interval (PI). The relative distance to the regression line was assessed. RESULTS: The neat CSF candidate CRM format was commutable for almost all method comparisons, except for the Simoa/MSD, Simoa/MS and MS/IBL where it was found just outside the 95% PI. However, the neat CSF was found within 5% relative distance to the regression line for MS/IBL, between 5% and 10% for Simoa/MS and between 10% and 15% for Simoa/MSD comparisons. CONCLUSIONS: The neat CSF candidate CRM format was commutable for 33 of 36 method comparisons, only one comparison more than expected given the 95% PI acceptance limit. We conclude that the neat CSF candidate CRM can be used for value assignment of the kit calibrators for the different Aβ42 methods.
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| 3. |
- De Meyer, Geert, et al.
(författare)
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Diagnosis-independent Alzheimer disease biomarker signature in cognitively normal elderly people.
- 2010
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Ingår i: Archives of neurology. - : American Medical Association (AMA). - 1538-3687 .- 0003-9942. ; 67:8, s. 949-56
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: To identify biomarker patterns typical for Alzheimer disease (AD) in an independent, unsupervised way, without using information on the clinical diagnosis. DESIGN: Mixture modeling approach. SETTING: Alzheimer's Disease Neuroimaging Initiative database. Patients or Other PARTICIPANTS: Cognitively normal persons, patients with AD, and individuals with mild cognitive impairment. MAIN OUTCOME MEASURES: Cerebrospinal fluid-derived beta-amyloid protein 1-42, total tau protein, and phosphorylated tau(181P) protein concentrations were used as biomarkers on a clinically well-characterized data set. The outcome of the qualification analysis was validated on 2 additional data sets, 1 of which was autopsy confirmed. RESULTS: Using the US Alzheimer's Disease Neuroimaging Initiative data set, a cerebrospinal fluid beta-amyloid protein 1-42/phosphorylated tau(181P) biomarker mixture model identified 1 feature linked to AD, while the other matched the "healthy" status. The AD signature was found in 90%, 72%, and 36% of patients in the AD, mild cognitive impairment, and cognitively normal groups, respectively. The cognitively normal group with the AD signature was enriched in apolipoprotein E epsilon4 allele carriers. Results were validated on 2 other data sets. In 1 study consisting of 68 autopsy-confirmed AD cases, 64 of 68 patients (94% sensitivity) were correctly classified with the AD feature. In another data set with patients (n = 57) with mild cognitive impairment followed up for 5 years, the model showed a sensitivity of 100% in patients progressing to AD. CONCLUSIONS: The mixture modeling approach, totally independent of clinical AD diagnosis, correctly classified patients with AD. The unexpected presence of the AD signature in more than one-third of cognitively normal subjects suggests that AD pathology is active and detectable earlier than has heretofore been envisioned.
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| 4. |
- De Meyer, Geert, et al.
(författare)
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Diagnosis-Independent Alzheimer Disease Biomarker Signature in Cognitively Normal Elderly People
- 2010
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Ingår i: Archives of Neurology. - 0003-9942. ; 67:8, s. 949-956
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Tidskriftsartikel (refereegranskat)abstract
- Objective: To identify biomarker patterns typical for Alzheimer disease (AD) in an independent, unsupervised way, without using information on the clinical diagnosis. Design: Mixture modeling approach. Setting: Alzheimer's Disease Neuroimaging Initiative database. Patients or Other Participants: Cognitively normal persons, patients with AD, and individuals with mild cognitive impairment. Main Outcome Measures: Cerebrospinal fluid derived p-amyloid protein 1-42, total tau protein, and phosphorylated tau(181p) protein concentrations were used as biomarkers on a clinically well-characterized data set. The outcome of the qualification analysis was validated on 2 additional data sets, 1 of which was autopsy confirmed. Results: Using the US Alzheimer's Disease Neuroimaging Initiative data set, a cerebrospinal fluid beta-amyloid protein 1-42/phosphorylated tau(181P) biomarker mixture model identified 1 feature linked to AD, while the other matched the "healthy" status. The AD signature was found in 90%, 72%, and 36% of patients in the AD, mild cognitive impairment, and cognitively normal groups, respectively. The cognitively normal group with the AD signature was enriched in apolipoprotein E 64 allele carriers. Results were validated on 2 other data sets. In 1 study consisting of 68 autopsy-confirmed AD cases, 64 of 68 patients (94% sensitivity) were correctly classified with the AD feature. In another. data set with patients (n=57) with mild cognitive impairment followed up for 5 years, the model showed a sensitivity of 100% in patients progressing to AD. Conclusions: The mixture modeling approach, totally independent of clinical AD diagnosis, correctly classified patients with AD. The unexpected presence of the AD signature in more than one-third of cognitively normal subjects suggests that AD pathology is active and detectable earlier than has heretofore been envisioned.
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| 5. |
- Hampel, Harald, et al.
(författare)
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Measurement of phosphorylated tau epitopes in the differential diagnosis of Alzheimer disease: a comparative cerebrospinal fluid study.
- 2004
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Ingår i: Archives of general psychiatry. - : American Medical Association (AMA). - 0003-990X. ; 61:1, s. 95-102
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Abnormal hyperphosphorylation of the microtubule-associated protein tau and its incorporation into neurofibrillary tangles are major hallmarks of the pathogenesis of Alzheimer disease (AD). Different tau phosphoepitopes can be sensitively detected in cerebrospinal fluid (CSF). OBJECTIVE: To compare the diagnostic accuracy of CSF concentrations of tau proteins phosphorylated at 3 pathophysiologically important epitopes (p-tau) to discriminate among patients with AD, nondemented control subjects, and patients with other dementias. DESIGN AND SETTING: Cross-sectional, bicenter, memory clinic-based studies. PARTICIPANTS: One hundred sixty-one patients with a clinical diagnosis of AD, frontotemporal dementia, dementia with Lewy bodies, or vascular dementia and 45 nondemented controls (N = 206). MAIN OUTCOME MEASURES: Levels of tau protein phosphorylated at threonine 231 (p-tau231), threonine 181 (p-tau181), and serine 199 (p-tau199). The CSF p-tau protein levels were measured using 3 different enzyme-linked immunosorbent assays. RESULTS: The mean CSF levels of the studied p-tau proteins were significantly elevated in patients with AD compared with the other groups. Applied as single markers, p-tau231and p-tau181 reached specificity levels greater than 75% between AD and the combined non-AD group when sensitivity was set at 85% or greater. Statistical differences between the assay performances are presented. Particularly, discrimination between AD and dementia with Lewy bodies was maximized using p-tau181at a sensitivity of 94% and a specificity of 64%, and p-tau231 maximized group separation between AD and frontotemporal dementia with a sensitivity of 88% and a specificity of 92%. Combinations of the 3 markers did not add discriminative power compared with the application as single markers. CONCLUSIONS: The p-tau proteins in CSF come closest to fulfilling the criteria of a biological marker of AD. There is a tendency for p-tau proteins to perform differently in the discrimination of primary dementia disorders from AD.
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| 6. |
- Hansson, Oskar, et al.
(författare)
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Evaluation of plasma Abeta(40) and Abeta(42) as predictors of conversion to Alzheimer's disease in patients with mild cognitive impairment.
- 2010
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Ingår i: Neurobiology of aging. - : Elsevier BV. - 1558-1497 .- 0197-4580. ; 31:3, s. 357-67
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Tidskriftsartikel (refereegranskat)abstract
- Numerous studies have shown a marked decrease of beta-amyloid(42) (Abeta(42)) in the cerebrospinal fluid (CSF) of patients with incipient Alzheimer's disease (AD). However, studies on Abeta in plasma are contradictory, and show very marginal differences between patients and controls. Here, we analyzed plasma samples using a new multiplex immunoassay for simultaneous analysis of Abeta(1-40), Abeta(n-40), Abeta(1-42), and Abeta(n-42). The plasma samples were obtained at baseline from two independent cohorts of patients with mild cognitive impairment (MCI) and age-matched controls. In the first cohort, 41% of the 117 MCI cases converted to AD during a clinical follow-up period of 4-7 years. In the second cohort, 14% of the 110 MCI subjects developed AD during a clinical follow-up period of 2-4 years. None of the plasma Abeta isoforms differed between MCI patients that subsequently developed AD and healthy controls or stable MCI patients. The Cox proportional hazards model did not reveal any differences in the probability of progression from MCI to AD related to plasma Abeta levels. In contrast, low levels of Abeta(1-42) in CSF were strongly associated with increased risk of future AD. The absence of a change in plasma Abeta in incipient AD, despite the marked change in CSF, may be explained by the lack of a correlation between the levels of Abeta(1-42) in CSF and plasma. In conclusion, the results show that CSF biomarkers are better predictors of progression to AD than plasma Abeta isoforms.
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| 7. |
- Höglund, Kina, 1976, et al.
(författare)
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Plasma levels of beta-amyloid(1-40), beta-amyloid(1-42), and total beta-amyloid remain unaffected in adult patients with hypercholesterolemia after treatment with statins.
- 2004
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Ingår i: Archives of neurology. - : American Medical Association (AMA). - 0003-9942. ; 61:3, s. 333-7
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Epidemiological studies suggest that statins reduce the risk of developing Alzheimer disease. Cell and animal experiments have revealed a connection between cholesterol metabolism and the processing of amyloid precursor protein. To our knowledge, the mechanism for statins in risk reduction of Alzheimer disease is unknown. OBJECTIVE: To test the effect of statin treatment on beta-amyloid (A beta) metabolism in humans. DESIGN: A prospective, randomized, dose-finding 36-week treatment trial with statins. Plasma samples were taken at baseline (week 0) and at weeks 6, 12, and 36. SETTING: Outpatient clinical study at a university hospital. PATIENTS: Thirty-nine patients who met the criteria for hypercholesterolemia. INTERVENTIONS: Patients were randomized to oral treatment with either simvastatin or atorvastatin calcium according to the following regimen: simvastatin, 40 mg/d, or atorvastatin, 20 mg/d, for 6 weeks; followed by simvastatin, 80 mg/d, or atorvastatin, 40 mg/d, for 6 weeks; and finally, simvastatin, 80 mg/d, or atorvastatin, 80 mg/d, for 24 weeks. MAIN OUTCOME MEASURES: Plasma levels of A beta(1-40) and A beta(1-42) were measured using 2 enzyme-linked immunosorbent assays, and total A beta was quantified by Western blotting. RESULTS: Treatment with both statins reduced total plasma cholesterol levels by 56% (P =.00). The plasma levels of A beta(1-40), A beta(1-42), and total A beta were stable in individual patients during the treatment period. No significant change in the level of A beta(1-40), A beta(1-42), or total A beta was found. CONCLUSION: This study questions the effect of statins on the processing of amyloid precursor protein in humans.
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| 8. |
- Vanderstichele, Hugo, et al.
(författare)
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Analytical performance and clinical utility of the INNOTEST PHOSPHO-TAU181P assay for discrimination between Alzheimer's disease and dementia with Lewy bodies.
- 2006
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Ingår i: Clinical chemistry and laboratory medicine : CCLM / FESCC. - 1434-6621. ; 44:12, s. 1472-80
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Total tau (T-tau) and beta-amyloid((1-42)) (Abeta(1-42)) levels in cerebrospinal fluid (CSF) can differentiate Alzheimer's disease (AD) from normal aging or depressive pseudo-dementia. Differential diagnosis from dementia with Lewy bodies (DLB) in clinical settings is difficult. METHODS: The analytical performance of the INNOTEST PHOSPHO-TAU(181P) assay was validated in terms of selectivity, sensitivity, specificity, precision, robustness, and stability. Clinical utility of the assay alone, or combined with T-tau and Abeta(1-42), for discrimination of AD (n=94) from patients suffering from DLB (n=60) or from age-matched control subjects (CS) (n=60) was assessed in a multicenter study. RESULTS: CSF concentrations of tau phosphorylated at threonine 181 (P-tau(181P)) in AD was significantly higher than in DLB and CS. Discriminant analysis, a classification tree, and logistic regression showed that P-tau(181P) was the most statistically significant single variable of the three biomarkers for discrimination between AD and DLB. CONCLUSIONS: P-tau(181P) quantification is a robust and reliable assay that may be useful in discriminating AD from DLB.
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| 9. |
- Zetterberg, Henrik, 1973, et al.
(författare)
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Intra-individual stability of CSF biomarkers for Alzheimer's disease over two years
- 2007
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Ingår i: Journal of Alzheimer's disease : JAD. - 1387-2877. ; 12:3, s. 255-60
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Tidskriftsartikel (refereegranskat)abstract
- This study examines the intra-individual stability of cerebrospinal fluid (CSF) biomarkers for Alzheimer's disease (AD) over 2 years in 83 patients with mild cognitive impairment (MCI) and 17 cognitively healthy control individuals. All participants underwent clinical and neuropsychological evaluation and lumbar puncture at baseline and after 2 years at a university hospital memory clinic. CSF was analyzed for total tau (T-tau), phospho-tau(181) (P-tau(181)) and amyloid-beta(1-42) (Abeta(1-42)). During the 2-year observational time, 12 MCI patients progressed to AD and 3 progressed to vascular dementia, while 68 remained stable. Baseline T-tau and P-tau(181) levels were elevated in the MCI-AD group as compared to the stable MCI patients and the control group (p<0.01), while baseline Abeta(1-42) levels were lower (p<0.001). Stable MCI patients were biochemically indistinguishable from controls. The biomarker levels at baseline and after 2 years showed Pearson R values between 0.81 and 0.91 (p<0.001) and coefficients of variation of 7.2 to 8.7%. In conclusion, intra-individual biomarker levels are remarkably stable over 2 years. Thus, even minor biochemical changes induced by treatment against AD should be detectable using these biomarkers, which bodes well for their usefulness as surrogate markers for drug efficacy in clinical trials.
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