Christoffer Rosén

Fluid biomarkers in Alzheimer's disease - current concepts

The diagnostic guidelines of Alzheimer’s disease (AD) have recently been updated to include brain imaging and cerebrospinal fluid (CSF) biomarkers, with the aim of increasing the certainty of whether a patient has an ongoing AD neuropathologic process or not. The CSF biomarkers total tau (T-tau), hyperphosphorylated tau (P-tau) and the 42 amino acid isoform of amyloid β (Aβ42) reflect the core pathologic features of AD, which are neuronal loss, intracellular neurofibrillary tangles and extracellular senile plaques. Since the pathologic processes of AD start decades before the first symptoms, these biomarkers may provide means of early disease detection. The updated guidelines identify three different stages of AD: preclinical AD, mild cognitive impairment (MCI) due to AD and AD with dementia. In this review, we aim to summarize the CSF biomarker data available for each of these stages. We also review results from blood biomarker studies. In summary, the core AD CSF biomarkers have high diagnostic accuracy both for AD with dementia and to predict incipient AD (MCI due to AD). Longitudinal studies on healthy elderly and recent cross-sectional studies on patients with dominantly inherited AD mutations have also found biomarker changes in cognitively normal at-risk individuals. This will be important if disease-modifying treatment becomes available, given that treatment will probably be most effective early in the disease. An important prerequisite for this is trustworthy analyses. Since measurements vary between studies and laboratories, standardization of analytical as well as pre-analytical procedures will be essential. This process is already initiated. Apart from filling diagnostic roles, biomarkers may also be utilized for prognosis, disease progression, development of new treatments, monitoring treatment effects and for increasing the knowledge about pathologic processes coupled to the disease. Hence, the search for new biomarkers continues. Several candidate biomarkers have been found in CSF, and although biomarkers in blood have been harder to find, some recent studies have presented encouraging results. But before drawing any major conclusions, these results need to be verified in independent studies.

CSF neurofilament light differs in neurodegenerative diseases and predicts severity and survival.

Objectives: We hypothesized that CSF neurofilament light (NFL) levels would be elevated in dementias with subcortical involvement, including vascular dementia (VaD), but less elevated in dementias primarily affecting gray matter structures, such as Alzheimer disease (AD), and that elevated CSF NFL would correlate with disease severity and shorter survival time irrespective of clinical diagnosis. Methods: We included 3,356 individuals with dementia who had CSF NFL analyzed in our laboratory between 2005 and 2012. Clinical diagnoses and Mini-Mental State Examination (MMSE) scores were obtained from the Swedish Dementia Registry, and in selected cases (n = 478), date of death from the Swedish Mortality Registry. Results: CSF NFL differed among clinical diagnoses, with the highest levels seen in frontotemporal dementia, VaD, and mixed AD and VaD. Early-onset AD (younger than 65 years) had the lowest levels. High CSF NFL correlated with low MMSE score and short survival time irrespective of diagnosis, and was also particularly evident in AD. Conclusions: CSF NFL differs among different neurodegenerative diseases and is especially high in dementias engaging subcortical brain regions, such as VaD and mixed AD and VaD, but also in frontotemporal dementia. The association of high CSF NFL levels with disease severity and short survival supports the notion that high CSF NFL levels indicate more aggressive disease processes.

Discriminatory Analysis of Biochip-Derived Protein Patterns in CSF and Plasma in Neurodegenerative Diseases

The role of biomarkers in neurodegenerative diseases has been emphasized by recent research. Future clinical demands for identifying diseases at an early stage may render them essential. The aim of this pilot study was to test the analytical performance of two multiplex assays of cerebral markers on a well-defined clinical material consisting of patients with various neurodegenerative diseases. We measured 10 analytes in plasma and cerebrospinal fluid (CSF) from 60 patients suffering from Alzheimers disease (AD), vascular dementia, frontotemporal dementia, dementia with Lewy bodies, or mild cognitive impairment, as well as 20 cognitively healthy controls. We used the Randox biochip-based Evidence Investigator™ system to measure the analytes. We found it possible to measure most analytes in both plasma and CSF, and there were some interesting differences between the diagnostic groups, although with large overlaps. CSF heart-type fatty acid-binding protein was increased in AD. Glial fibrillary acidic protein and neutrophil gelatinase-associated lipocalin in CSF and D-dimer in plasma were elevated in patients with cerebrovascular disease. A multivariate statistical analysis revealed that the pattern of analytes could help to differentiate the conditions, although more studies are required to verify this.

Diagnostic Performance of Cerebrospinal Fluid Total Tau and Phosphorylated Tau in Creutzfeldt-Jakob Disease Results From the Swedish Mortality Registry

IMPORTANCE Identifying a clinical distinction between the invariably lethal prion disease Creutzfeldt-Jakob disease (CJD) and nonprion rapidly progressive dementias is important and sometimes difficult; thus, reliable tools for diagnosis are in great demand. OBJECTIVE To test the diagnostic performance of dementia cerebrospinal fluid (CSF) biomarkers total tau (T-tau), phosphorylated tau (P-tau), and the T-tau to P-tau ratio for CJD by analyzing the results from a large database of routine clinical samples in combination with diagnosis information from the Swedish Mortality Registry. DESIGN, SETTING, AND PARTICIPANTS This was a retrospective cohort study. We cross-referenced the Swedish Mortality Registry with a data set of CSF measurements of T-tau and P-tau performed in routine clinical testing at the Clinical Neurochemistry Laboratory of the Sahlgrenska University Hospital, which serves most of Sweden. The data set consisted of 9765 deceased individuals with CSF measures, including 93 with CJD, with 52 autopsy-verified samples (56%). MAIN OUTCOMES AND MEASURES For each patient, T-tau and P-tau levels in CSF were measured and the T-tau to P-tau ratio was calculated. Biomarker levels (adjusted for age and sex) were analyzed in relation to the recorded cause of death and time of death. We specifically tested a previously defined CJD biomarker profile (T-tau >1400 ng/L and T-tau to P-tau-ratio >25). RESULTS Patients who died of CJD had elevated CSF T-tau levels and T-tau to P-tau ratio, but not elevated CSF P-tau levels, compared with patients who died of Alzheimer disease (AD) and other dementias. The previously defined biomarker profile had a specificity of 99.0%, a sensitivity of 78.5%, and a positive likelihood ratio of 79.9. When tested against common differential diagnoses, the sensitivity, specificity, and positive likelihood ratio of this profile was 78.5%, 99.6%, and 196.6, respectively, in relation to AD and 78.5%, 99.3%, and 109.3, respectively, in relation to other dementias. In CJD individuals (n = 30) with repeated measurements, but not in those with AD (n = 242) or other dementias (n = 258), T-tau levels and T-tau to P-tau ratios increased over time. CONCLUSIONS AND RELEVANCE In this routine clinical setting, the combination of increased T-tau levels and increased T-tau to P-tau ratios in CJD patients has a very high specificity against important differential diagnoses to CJD and may serve as a clinically useful diagnostic test.

Cerebrospinal Fluid Profiles of Amyloid beta-Related Biomarkers in Alzheimer's Disease

The amyloid cascade hypothesis on the pathogenesis of Alzheimer’s disease (AD) states that amyloid β (Aβ) accumulation in the brain is a key factor that initiates the neurodegenerative process. Aβ is generated from amyloid precursor protein (APP) through sequential cleavages by BACE1 (the major β-secretase in the brain) and γ-secretase. The purpose of this study was to characterize APP metabolism in vivo in AD patients versus cognitively healthy subjects by examining alterations in cerebrospinal fluid (CSF) biomarkers. We measured BACE1 activity and concentrations of α- and β-cleaved soluble APP (sAPPα and sAPPβ, respectively) and Aβ40 in CSF, biomarkers that all reflect the metabolism of APP, in 75 AD patients and 65 cognitively healthy controls. These analytes were also applied in a multivariate model to determine whether they provided any added diagnostic value to the core CSF AD biomarkers Aβ42, T-tau, and P-tau. We found no significant differences in BACE1 activity or sAPPα, sAPPβ, and Aβ40 concentrations between AD patients and controls. A multivariate model created with all analytes did not improve the separation of AD patients from controls compared with using the core AD biomarkers alone, highlighting the strong diagnostic performance of Aβ42, T-tau, and P-tau for AD. However, AD patients in advanced clinical stage, as determined by low MMSE score (≤20), had lower BACE1 activity and sAPPα, sAPPβ, and Aβ40 concentrations than patients with higher MMSE score, suggesting that these markers may be related to the severity of the disease.

Increased Levels of Chitotriosidase and YKL-40 in Cerebrospinal Fluid from Patients with Alzheimer's Disease

Background: The cerebrospinal fluid (CSF) biomarkers total tau, abnormally phosphorylated tau and amyloid β 1-42 are strongly associated with Alzheimers disease (AD). Apart from the pathologic hallmarks that these biomarkers represent, other processes such as inflammation and microglial activation are present in the brains of patients with AD. New biomarkers related to these processes could be valuable for the diagnosis and follow-up of AD patients and for the evaluation of inflammation-related pathologies. Aim: The aim of this study was to evaluate the association of inflammatory CSF biomarkers with AD. Methods: Twenty-five AD patients and 25 controls who had a pathological and normal CSF profile of the core AD biomarkers, respectively, were included in this study. CSF levels of chitotriosidase, YKL-40 (also known as chitinase-3-like protein 1) and monocyte chemoattractant protein-1 (MCP-1) were quantified and the levels compared between the groups. Results: AD patients had increased CSF levels of chitotriosidase and YKL-40 (both approximately twice higher than in controls), while the levels of MCP-1 were similar in the AD and control groups. Conclusion: The results indicate that chitotriosidase and YKL-40 may be helpful for the evaluation of cerebral inflammatory activity in AD patients.

Cerebrospinal fluid tau and amyloid-β1-42 in patients with dementia.

Progressive cognitive decline in combination with a cerebrospinal fluid biomarker pattern of low levels of amyloid-β1-42 and high levels of total tau and phosphorylated tau is typical of Alzheimers disease. However, several neurodegenerative disorders may overlap with Alzheimers disease both in regards to clinical symptoms and neuropathology. In a uniquely large cohort of dementia patients, we examined the associations of cerebrospinal fluid biomarkers for Alzheimers disease molecular pathology with clinical dementia diagnoses and disease severity. We cross-referenced the Swedish Dementia Registry with the clinical laboratory database at the Sahlgrenska University Hospital. The final data set consisted of 5676 unique subjects with a clinical dementia diagnosis and a complete set of measurements for cerebrospinal fluid amyloid-β1-42, total tau and phosphorylated tau. In cluster analysis, disregarding clinical diagnosis, the optimal natural separation of this data set was into two clusters, with the majority of patients with early onset Alzheimers disease (75%) and late onset Alzheimers disease (73%) assigned to one cluster and the patients with vascular dementia (91%), frontotemporal dementia (94%), Parkinsons disease dementia (94%) and dementia with Lewy bodies (87%) to the other cluster. Frontotemporal dementia had the highest cerebrospinal fluid levels of amyloid-β1-42 and the lowest levels of total tau and phosphorylated tau. The highest levels of total tau and phosphorylated tau and the lowest levels of amyloid-β1-42 and amyloid-β1-42:phosphorylated tau ratios were found in Alzheimers disease. Low amyloid-β1-42, high total tau and high phosphorylated tau correlated with low Mini-Mental State Examination scores in Alzheimers disease. In Parkinsons disease dementia and vascular dementia low cerebrospinal fluid amyloid-β1-42 was associated with low Mini-Mental State Examination score. In the vascular dementia, frontotemporal dementia, dementia with Lewy bodies and Parkinsons disease dementia groups 53%, 34%, 67% and 53% of the subjects, respectively had abnormal amyloid-β1-42 levels, 41%, 41%, 28% and 28% had abnormal total tau levels, and 29%, 28%, 25% and 19% had abnormal phosphorylated tau levels. Cerebrospinal fluid biomarkers were strongly associated with specific clinical dementia diagnoses with Alzheimers disease and frontotemporal dementia showing the greatest difference in biomarker levels. In addition, cerebrospinal fluid amyloid-β1-42, total tau, phosphorylated tau and the amyloid-β1-42:phosphorylated tau ratio all correlated with poor cognitive performance in Alzheimers disease, as did cerebrospinal fluid amyloid-β1-42 in Parkinsons disease dementia and vascular dementia. The results support the use of cerebrospinal fluid biomarkers to differentiate between dementias in clinical practice, and to estimate disease severity.

CSF in Alzheimer's Disease

Alzheimers disease (AD) is a progressive brain amyloidosis that injures brain regions involved in memory consolidation and other cognitive functions. Neuropathologically, the disease is characterized by accumulation of a 42-amino acid protein called amyloid beta, and N-terminally truncated fragments thereof, in extracellular senile plaques together with intraneuronal inclusions of hyperphosphorylated tau protein in neurofibrillary tangles, and neuronal and axonal degeneration and loss. Clinical chemistry tests for these pathologies have been developed for use on cerebrospinal fluid samples. Here, we review what these markers have taught us on the disease process in AD and how they can be implemented in routine clinical chemistry. We also provide an update on new marker development and ongoing analytical standardization effort.

Cerebrospinal fluid biomarkers for pathological processes in Alzheimer's disease.

Purpose of review To review the rationale behind and the use of cerebrospinal fluid (CSF) biomarkers in Alzheimers disease (AD). Established as well as new candidate biomarkers will be covered. Recent findings AD is a complex disorder and the AD brain is characterized by multiple pathological processes, in addition to well-described plaque and tangle diseases. Recent studies have tried to address this by evaluating biomarkers related to features such as neuroinflammation, oxidative stress, microglial activation and synaptic degeneration, with some positive results. Summary The CSF biomarkers total tau, phosphorylated-tau and the 42 amino acid isoform of amyloid beta reflect core elements of AD, that is, axonal degeneration, tangle disease and senile plaques, have been thoroughly tested and provide high diagnostic accuracy in the discrimination of patients with AD as compared with cognitively normal controls. They are also highly predictive of AD with dementia in patients with mild cognitive impairment, and have been included in new diagnostic criteria. New biomarkers may add to their diagnostic performance. Other potential fields of use include the monitoring of disease progression or pharmacodynamic drug effects. A common denominator for the candidate biomarkers is the need for validation in further studies to clarify their potential.

Cerebrospinal fluid biomarkers in cardiac arrest survivors.

AIM The aim of this study was to investigate the levels of various cerebrospinal fluid (CSF) biomarkers related to neuronal damage, inflammation and amyloid β (Aβ) metabolism in patients resuscitated after an out-of-hospital cardiac arrest (CA). METHODS CSF levels of neurofilament light protein (NFL), total tau (T-tau), hyperphosphorylated tau (P-tau), YKL-40, Aβ38, Aβ40, Aβ42, soluble amyloid precursor protein α and β (sAPPα and sAPPβ) were measured in 21 patients approximately two weeks after CA and in 21 age-matched neurologically healthy controls. The biomarker levels were also compared between patients with good and poor long-term clinical outcome according to Glasgow Outcome Scale (GOS), activities of daily living (ADL) and mini-mental state examination (MMSE), measuring neurologic function, daily functioning and cognitive function, respectively. RESULTS Patients with CA had a very marked increase in the CSF levels of NFL, T-tau and YKL-40 as compared with controls. The levels were increased at about 1200, 700 and 100%, respectively. NFL and T-tau were significantly higher in patients with poor outcome according to all three outcome measures. Patients with poor outcome according to GOS and ADL had higher levels of YKL-40. Levels of Aβ38, Aβ40, Aβ42, sAPPα and sAPPβ were lower in patients with a low MMSE score. P-tau was not significantly altered. CONCLUSIONS Biomarkers reflecting neuronal damage and inflammation, but not so much Aβ metabolism, were significantly altered in patients after a CA, and the changes were more pronounced in the groups with poor outcome. This calls for future larger studies to determine the prognostic potential of these biomarkers.