The diagnostic value of cerebrospinal fluid tau protein in dementing and nondementing neuropsychiatric disorders

Cerebrospinal Fluid Biomarkers for Alzheimer's Disease in the Era of Disease-Modifying Treatments

Correct in vivo diagnosis of Alzheimer’s disease (AD) helps to avoid administration of disease-modifying treatments in non-AD patients, and allows the possible use of such treatments in clinically atypical AD patients. Cerebrospinal fluid (CSF) biomarkers offer a tool for AD diagnosis. A reduction in CSF β-amyloid (marker of amyloid plaque burden), although compatible with Alzheimer’s pathological change, may also be observed in other dementing disorders, including vascular cognitive disorders due to subcortical small-vessel disease, dementia with Lewy bodies and normal-pressure hydrocephalus. Thus, for the diagnosis of AD, an abnormal result of CSF β-amyloid may not be sufficient, and an increase in phospho-tau (marker of tangle pathology) is also required in order to confirm AD diagnosis in patients with a typical amnestic presentation and reveal underlying AD in patients with atypical or mixed and diagnostically confusing clinical presentations.

Cerebrospinal fluid biomarkers and cognitive status in differential diagnosis of frontotemporal dementia and Alzheimer's disease

Objective

This study aimed to determine the most appropriate cognitive and cerebrospinal fluid (CSF) biomarker setting to distinguish frontotemporal dementia (FTD) from Alzheimer’s disease (AD).

Method

Patients with FTD, those with AD, and those without dementia were enrolled in this study. CSF amyloid-ß 42 (Aß42), total (t)-tau, and phosphorylated (p)-tau concentrations were determined by enzyme-linked immunosorbent assays. Cognition was evaluated by the Mini-Mental State Examination (MMSE) and its domain scores. The associations of CSF biomarkers with cognitive measures were examined using regression models and the diagnostic value of CSF biomarkers was determined by receiver operating characteristics curves.

Results

CSF Aß42 levels were lower, whereas t-tau/Aß42 and p-tau/Aß42 ratios were higher in patients with AD compared with those with FTD. Some MMSE domain scores were different in FTD and AD, but they did not improve the ability to distinguish between the two pathologies. Poor temporal orientation scores were associated with low Aß42 levels only in patients with FTD. The p-tau/Aß42 ratio reached sufficient levels of sensitivity and specificity to discriminate FTD with primary progressive aphasia from AD.

Conclusions

The ratio of CSF p-tau/Aß42 is a sensitive and specific biomarker for discriminating patients with primary progressive aphasia from those with AD.

Cerebrospinal Fluid Biomarkers for the Differential Diagnosis between Alzheimer's Disease and Frontotemporal Lobar Degeneration: Systematic Review, HSROC Analysis, and Confounding Factors

BACKGROUND

Differential diagnosis in dementia is at present one of the main challenges both in clinical practice and research. Cerebrospinal fluid (CSF) biomarkers are included in the current diagnostic criteria of Alzheimer's disease (AD) but their clinical utility is still unclear.

OBJECTIVE

We performed a systematic review of studies analyzing the diagnostic performance of CSF Aβ42, total tau (t-tau), and phosphorylated tau (p-tau) in the discrimination between AD and frontotemporal lobar degeneration (FTLD) dementias.

METHODS

The following electronic databases were consulted until May 2016: Medline and PreMedline, EMBASE, PsycInfo, CINAHL, Cochrane Library, and CRD. For the first-time in the field, a Hierarchical Summary Receiver Operating Characteristic (HRSOC) model was applied, which avoids methodological problems of meta-analyses based on summary points of sensitivity and specificity values. We also investigated relevant confounders of CSF biomarkers' diagnostic performance such as age, disease duration, and global cognitive impairment.

RESULTS

The p-tau/Aβ42 ratio showed the best diagnostic performance. No statistically significant effects of the confounders were observed. Nonetheless, the p-tau/Aβ42 ratio may be especially indicated for younger patients. P-tau may be preferable for less cognitively impaired patients (high MMSE scores) and the t-tau/Aβ42 ratio for more cognitively impaired patients (low MMSE scores).

CONCLUSION

The p-tau/Aβ42 ratio has potential for being implemented in the clinical routine for the differential diagnosis between AD and FTLD. It is of utmost importance that future studies report information on confounders such as age, disease duration, and cognitive impairment, which should also stimulate understanding of the role of these factors in disease mechanisms and pathophysiology.

Tau in Late-Life Depression: A Systematic Review and Meta-Analysis

A lifetime history of major depressive disorder (MDD) increases the risk of developing Alzheimer's disease, of which neurofibrillary tangles due to abnormal tau proteins are a hallmark. We systematically reviewed the literature on tau in MDD and identified 49 relevant articles spanning a number of modalities, including cerebrospinal fluid (CSF) analysis, positron emission tomography, and clinicopathological correlation. We compared CSF total and phosphorylated tau proteins in MDD and controls using a meta-analytic approach. We found no difference in total or phosphorylated tau in MDD. We also found no difference in a comparison of a subgroup excluding studies with significant age differences. Positron emission tomography studies lacked specificity. Clinicopathological studies failed to associate neurofibrillary tangles with MDD. The available data on tau in MDD is limited. The involvement of tau in a subset of MDD cannot be ruled out and requires prospective exploration.

Update on Vascular Cognitive Impairment Associated with Subcortical Small-Vessel Disease

Subcortical small-vessel disease (SSVD) is a disorder well characterized from the clinical, imaging, and neuropathological viewpoints. SSVD is considered the most prevalent ischemic brain disorder, increasing in frequency with age. Vascular risk factors include hypertension, diabetes, hyperlipidemia, elevated homocysteine, and obstructive sleep apnea. Ischemic white matter lesions are the hallmark of SSVD; other pathological lesions include arteriolosclerosis, dilatation of perivascular spaces, venous collagenosis, cerebral amyloid angiopathy, microbleeds, microinfarcts, lacunes, and large infarcts. The pathogenesis of SSVD is incompletely understood but includes endothelial changes and blood-brain barrier alterations involving metalloproteinases, vascular endothelial growth factors, angiotensin II, mindin/spondin, and the mammalian target of rapamycin pathway. Metabolic and genetic conditions may also play a role but hitherto there are few conclusive studies. Clinical diagnosis of SSVD includes early executive dysfunction manifested by impaired capacity to use complex information, to formulate strategies, and to exercise self-control. In comparison with Alzheimer's disease (AD), patients with SSVD show less pronounced episodic memory deficits. Brain imaging has advanced substantially the diagnostic tools for SSVD. With the exception of cortical microinfarcts, all other lesions are well visualized with MRI. Diagnostic biomarkers that separate AD from SSVD include reduction of cerebrospinal fluid amyloid-β (Aβ)42 and of the ratio Aβ42/Aβ40 often with increased total tau levels. However, better markers of small-vessel function of intracerebral blood vessels are needed. The treatment of SSVD remains unsatisfactory other than control of vascular risk factors. There is an urgent need of finding targets to slow down and potentially halt the progression of this prevalent, but often unrecognized, disorder.

Biochemical markers in vascular cognitive impairment associated with subcortical small vessel disease - A consensus report

Background

Vascular cognitive impairment (VCI) is a heterogeneous entity with multiple aetiologies, all linked to underlying vascular disease. Among these, VCI related to subcortical small vessel disease (SSVD) is emerging as a major homogeneous subtype. Its progressive course raises the need for biomarker identification and/or development for adequate therapeutic interventions to be tested. In order to shed light in the current status on biochemical markers for VCI-SSVD, experts in field reviewed the recent evidence and literature data.

Method

The group conducted a comprehensive search on Medline, PubMed and Embase databases for studies published until 15.01.2017. The proposal on current status of biochemical markers in VCI-SSVD was reviewed by all co-authors and the draft was repeatedly circulated and discussed before it was finalized.

Results

This review identifies a large number of biochemical markers derived from CSF and blood. There is a considerable overlap of VCI-SSVD clinical symptoms with those of Alzheimer’s disease (AD). Although most of the published studies are small and their findings remain to be replicated in larger cohorts, several biomarkers have shown promise in separating VCI-SSVD from AD. These promising biomarkers are closely linked to underlying SSVD pathophysiology, namely disruption of blood-CSF and blood–brain barriers (BCB-BBB) and breakdown of white matter myelinated fibres and extracellular matrix, as well as blood and brain inflammation. The leading biomarker candidates are: elevated CSF/blood albumin ratio, which reflects BCB/BBB disruption; altered CSF matrix metalloproteinases, reflecting extracellular matrix breakdown; CSF neurofilment as a marker of axonal damage, and possibly blood inflammatory cytokines and adhesion molecules. The suggested SSVD biomarker deviations contrasts the characteristic CSF profile in AD, i.e. depletion of amyloid beta peptide and increased phosphorylated and total tau.

Conclusions

Combining SSVD and AD biomarkers may provide a powerful tool to identify with greater precision appropriate patients for clinical trials of more homogeneous dementia populations. Thereby, biomarkers might promote therapeutic progress not only in VCI-SSVD, but also in AD.

How many biomarkers to discriminate neurodegenerative dementia?

A number of cerebrospinal fluid (CSF) biomarkers are currently used for the diagnosis of dementia. Opposite changes in the level of amyloid-β(1-42) versus total tau and phosphorylated-tau181 in the CSF reflect the specific pathology of Alzheimer's disease (AD) in the brain. This panel of biomarkers has proven to be effective to differentiate AD from controls and from the major types of neurodegenerative dementia, and to evaluate the progression from mild cognitive impairment to AD. In the absence of specific biomarkers reflecting the pathologies of the other most common forms of dementia, such as Lewy Body disease, Frontotemporal lobar degeneration, Creutzfeldt-Jakob disease, etc., the evaluation of biomarkers of AD pathology is used, attempting to exclude rather than to confirm AD. Other biomarkers included in the common clinical practice do not clearly relate to the underlying pathology: progranulin (PGRN) is a selective marker of frontotemporal dementia with mutations in the PGRN gene; the 14-3-3 protein is a highly sensitive and specific marker for Creutzfeldt-Jakob disease, but has to be used carefully in differentiating rapid progressive dementia; and α-synuclein is an emerging candidate biomarker of the different forms of synucleinopathy. This review summarizes several biomarkers of neurodegenerative dementia validated based on the neuropathological processes occurring in brain tissue. Notwithstanding the paucity of pathologically validated biomarkers and their high analytical variability, the combinations of these biomarkers may well represent a key and more precise analytical and diagnostic tool in the complex plethora of degenerative dementia.

Evaluation of coexistence of Alzheimer's disease in idiopathic normal pressure hydrocephalus using ELISA analyses for CSF biomarkers

BACKGROUND

We investigated levels of the β-amyloid 1-42 (Aβ42), total tau protein (T-tau) and tau phosphorylated at position threonine 181 (P-tau) in cerebrospinal fluid (CSF) of idiopathic normal pressure hydrocephalus (iNPH) patients and tried to find their clinical implications in the evaluation and treatment of iNPH.

METHOD

Twenty-five possible iNPH patients were prospectively enrolled and their CSF was collected to analyze levels of Aβ42, T-tau and P-tau using ELISA method. Gait disturbance, urinary incontinence, and cognitive impairment were semi-quantified and detailed neuropsychological (NP) test was performed.

RESULT

Eight iNPH patients were classified into the lower CSF Aβ42 group and 17 patients were classified into the higher CSF Aβ42 group. There was no difference in the iNPH grading score and its improvement after LP between the two groups. The lower CSF Aβ42 group showed more deficits in attention, visuospatial function and verbal memory in the baseline NP test and less improvement in phonemic categorical naming and frontal inhibitory function after LP.

CONCLUSIONS

Our study suggested that concomitant AD in iNPH patients might contribute to lumbar puncture or shunt unresponsiveness, especially in the field of cognitive dysfunction.

Cerebrospinal fluid τ protein in differential diagnosis of Alzheimer's disease and vascular dementia in Chinese population: a meta-analysis

BACKGROUND

To assess whether biomarker τ protein could differentiate between Alzheimer's disease (AD) and vascular dementia (VaD).

METHODS

We conducted a comprehensive search to identify studies on τ protein, patients with AD, and patients with VaD. Cerebrospinal fluid (CSF) τ protein levels were compared to discriminate among patients with AD, healthy controls, and patients with VaD by a meta-analysis.

RESULTS

Patients with AD exhibit significantly higher CSF τ protein levels than healthy controls or patients with VaD in the Chinese population.

CONCLUSION

Our findings suggested that CSF τ protein levels were found to be significantly associated with AD in the Chinese population. Measurement of τ protein could help in attenuating the strict distinction between AD and VaD.

Cerebrospinal fluid tau levels predict prognosis in non-inherited frontotemporal dementia

BACKGROUND

The course of frontotemporal dementia (FTD) is heterogeneous and no predictors of survival are currently available. Cerebrospinal fluid (CSF) tau dosage has been demonstrated to be useful in predicting outcome over time in a number of neurological disorders.

OBJECTIVE

To assess CSF tau levels in FTD and to evaluate their prognostic value.

METHODS

Seventy-seven FTD patients with no mutations in known causative genes were consecutively enrolled, and CSF tau and phospho-tau levels analysed. Each patient was reassessed over time, and survival (i.e. death/bedridden and otherwise) was evaluated. The survival analysis was carried out by Cox proportional hazards regression models.

RESULTS

Patients with high CSF tau levels (≥400 pg/ml) had shorter survival than those with low CSF tau levels [hazard ratio (HR) = 3.406; 95% CI: 1.151-10.077; Wald χ(2) = 4.902; d.f. = 1; p = 0.027]. The association between tau levels and survival probability was confirmed after adjusting for age, gender, clinical phenotype and FTD clinical dementia rating at enrolment (HR = 3.769; 95% CI: 1.143-12.433; Wald χ(2) = 4.748; d.f. = 1; p = 0.029). Neither demographic or clinical characteristics nor CSF phospho-tau levels or apolipoprotein E genotype were significantly associated with prognosis.

CONCLUSIONS

This study argues that CSF tau levels may be considered in FTD to predict patients' outcome. Establishing in vivo prognostic biomarkers is mandatory to define homogeneous groups for inclusion in future clinical trials and to monitor the effectiveness of future therapeutic approaches.

Cerebrospinal fluid β-amyloid 1-42 correlates with rate of progression in Alzheimer's disease

Emerging treatment options targeting the pathogenetic mechanisms in Alzheimer's disease (AD) and the need to monitor efficacy during treatment trials necessitate the use of biomarkers, which not only may facilitate early and reliable diagnosis, but may also assist in the stratification of patient populations according to their rate of progression. The objective of the present study is to examine whether demographic and cerebrospinal fluid (CSF) parameters at initial evaluation [total tau, tau phosphorylated at threonine-181 and amyloid-beta(1-42) (Aβ42)] can be used to discriminate between slow and rapid progressors in patients with AD. A total of 74 AD patients were included in the study. Patients recruited were divided into slow and rapid progressors according to their Mini-Mental Status Examination (MMSE) score decline before evaluation. Patients with a drop rate of >4/year were considered rapid progressors. Commercially available ELISA kits were used for measuring CSF biomarkers. Comparisons were performed using analysis of covariance. Significantly lower Aβ42 levels in the CSF were found in rapid (mean 392 pg/ml) as compared to slow progressors (mean 453 pg/ml), with a p value of 0.042. The results of the present study suggest that levels of the Aβ42 peptide may be related to the rate of disease progression. Further studies with a prospective design are needed in order to test the possible predictive value of CSF Aβ42 analysis.

Amyloid-β and τ biomarkers in Parkinson's disease-dementia

Dementia is a frequent and devastating non-motor complication of advanced Parkinson's disease (PD). There is growing evidence of a synergistic role of Alzheimer's-type brain lesions containing τ and amyloid-β (Aβ) proteins and cortical Lewy aggregates in PD-related dementia (PDD). Therefore, biomarkers of both τ and Aβ may be seen as diagnostic and predictive markers of PDD. Here, we review the available studies in PD and PDD using cerebrospinal fluid (CSF) total τ, phospho-τ, and/or Aβ levels, and PET probes targeting Alzheimer's-type lesions. Overall, high CSF τ and phospho-τ levels and/or low CSF Aβ levels have been found in part of PDD patients, and a longitudinal study has found greater worsening in cognitive performance over time in non-demented PD patients with low baseline CSF Aβ levels. Few studies are available on the use of PET imaging in PD, all of them using the Pittsburgh B compound (PIB), and with figures of about 30% of scans with PIB uptake in the AD-range in PDD. We conclude that these CSF and PET markers deserve further evaluation as candidate biomarkers of dementia in PD. According to this, we are currently undertaking a longitudinal project on the predictive value of dementia of the combined use of CSF τ and Aβ and (18)F-FDDNP PET in PD.

Tau and p-tau as CSF biomarkers in dementia: a meta-analysis

BACKGROUND

To evaluate the value of total tau (tau) and phosphorylated tau (p-tau) in cerebrospinal fluid (CSF) in the differential diagnosis of dementia, more specifically: dementia with Lewy Bodies (DLB), frontotemporal lobar degeneration (FTLD), vascular dementia (VaD), and Creutzfeldt-Jacob disease (CJD).

METHODS

A systematic literature search was performed to identify studies on tau and p-tau in DLB, FTLD, VaD and CJD. Tau concentrations were compared to healthy controls and to subjects with Alzheimer's disease (AD) using random effect meta-analysis. Outcome measures were Cohen's delta, sensitivity and specificity.

RESULTS

Compared to controls, tau concentrations are moderately elevated in DLB, FTLD and VaD, while p-tau concentrations are only slightly elevated in DLB and not elevated in FTLD and VaD. Compared to AD, lower tau concentrations differentiated DLB with a sensitivity of 73% and a specificity of 90%, FTLD with sensitivity and specificity of 74%, and VaD with a sensitivity of 73% and a specificity of 86%. Relative to AD, lower p-tau values differentiated FTLD with a sensitivity of 79% and specificity of 83%, and VaD with a sensitivity of 88% and a specificity of 78%. CJD is characterized by extremely elevated tau concentrations with a sensitivity of 91% and a specificity of 98% vs. AD.

CONCLUSIONS

CSF tau concentrations in DLB, FTLD and VaD are intermediate between controls and AD patients. Overlap with both controls and AD patients results in insufficient diagnostic accuracy, and the development of more specific biomarkers for these disorders is needed. CJD is characterized by extremely increased tau values, resulting in a sensitivity and specificity that exceeds 90%.

Problems associated with fluid biomarkers for Parkinson's disease

This article focuses on biochemical markers that may be used in the diagnostics of Parkinson's disease and associated disorders, and to identify early cases and stratify patients into subgroups. We present an updated account of some currently available candidate fluid biomarkers, and discuss their diagnostic performance and limitations. We also discuss some of the general problems with Parkinson's disease biomarkers and possible ways of moving forward. It may be concluded that a diagnostically useful fluid biomarker for Parkinson's disease is yet to be identified. However, some interesting candidates exist and may prove useful in the future, alone or when analyzed together in patterns.

CSF Biomarkers Profile in CADASIL-A Model of Pure Vascular Dementia: Usefulness in Differential Diagnosis in the Dementia Disorder

Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy (CADASIL) is considered a model of pure vascular dementia (VD) because it occurs in young adults unlikely to have concomitant age and Alzheimer's Disease-(AD-) related pathology. CSF levels of β-amyloid 1-42 (Aβ42), total tau protein (t-tau), and phosphorylated tau-protein (p-tau), well accepted biomarkers of AD, were evaluated in 10 CADASIL patients, 22 AD patients, and 17 healthy age-matched subjects. Innotest β-amyloid 1-42, Innotest hTAU-Ag, and Innotest Phospho-tau 181p sandwich enzyme-linked immunoassay were used to determine CSF biomarkers levels. A case-control statistical analysis was carried out. CSF Aβ42 levels were significantly lower in CADASIL patients and considerable overlap with AD whereas t-tau and p-tau levels were normal and significantly different with respect to AD. A significant altered CSF biomarkers profile in a pure VD supports the use of CSF Aβ42, t-tau, and p-tau levels in the differential diagnosis of VD and AD.

Diagnostic cerebrospinal fluid biomarkers for Parkinson's disease: a pathogenetically based approach

The inaccuracy of the early diagnosis of Parkinson's disease (PD) has been a major incentive for studies aimed at the identification of biomarkers. Brain-derived cerebrospinal fluid (CSF) proteins are potential biomarkers considering the major role that proteins play in PD pathogenesis. In this review, we discuss the current hypotheses about the pathogenesis of PD and identify the most promising candidate biomarkers among the CSF proteins studied so far. The list of potential markers includes proteins involved in various pathogenetic processes, such as oxidative stress and protein aggregation. This list will undoubtedly grow in the near future by application of CSF proteomics and subsequent validation of identified proteins. Probably a single biomarker will not suffice to reach high sensitivity and specificity, because PD is pathogenetically heterogeneous and shares etiological factors with other neurodegenerative diseases. Furthermore, identified candidate biomarkers will have to be thoroughly validated before they can be implemented as diagnostic aids.

Neurochemical biomarkers in the differential diagnosis of movement disorders

In recent years, the neurochemical analysis of neuronal proteins in cerebrospinal fluid (CSF) has become increasingly accepted for the diagnosis of neurodegenerative dementia diseases such as Alzheimer's disease and Creutzfeldt-Jakob disease. CSF surrounds the central nervous system, and in the composition of CSF proteins one finds brain-specific proteins that are prioritized from blood-derived proteins. Levels of specific CSF proteins could be very promising biomarkers for central nervous system diseases. We need the development of more easily accessible biomarkers, in the blood. In neurodegenerative diseases with and without dementia, studies on CSF and blood proteins have investigated the usefulness of biomarkers in differential diagnosis. The clinical diagnoses of Parkinson's disease, dementia with Lewy bodies, multiple system atrophy, progressive supranuclear palsy, and corticobasal degeneration still rely mainly on clinical symptoms as defined by international classification criteria. In this article, we review CSF biomarkers in these movement disorders and discuss recent published reports on the neurochemical intra vitam diagnosis of neurodegenerative disorders (including recent CSF alpha-synuclein findings).

Diagnostic value of CSF biomarker profile in frontotemporal lobar degeneration

BACKGROUND

Cerebrospinal fluid (CSF) biomarkers have been increasingly studied in dementia clinical and differential diagnosis.

METHODS

We assessed levels of total tau protein (tauT), tau phosphorylated at threonine 181 (tau P-181), and beta-amyloid1-42 (A beta 42) in 34 patients with frontotemporal lobar degeneration (FTLD), 76 Alzheimer disease (AD) cases, and 93 controls (CTRL). Double sandwich enzyme-linked immunosorbent assays (Innogenetics) were used for measurements.

RESULTS

Total tau was significantly increased and A beta 42 decreased in FTLD and AD patients as compared with CTRL. CSF tau P-181 levels were significantly increased only in AD. The tauT/A beta 42 ratio successfully discriminated FTLD from CTRL with a 86.7% specificity and 80.6% sensitivity, whereas the tauT alone was more specific (95.7%) but less sensitive (64.75%). For the discrimination of FTLD from AD, tauT/A beta 42 ratio was better (90.3% sensitivity and 64.5% specificity) compared with the other biomarkers alone or in combination, whereas tau P-181 was less sensitive but more specific (68.4% and 85.7%, respectively). Subtype analysis revealed that the most AD-like profile of biomarkers were observed in FTLD with motor neuron signs, whereas the most non-AD profile were observed in patients with primary progressive aphasia.

CONCLUSIONS

Combined analysis of CSF biomarkers may be useful for the best possible antemortem discrimination of FTLD from AD.

Progressive supranuclear palsy and corticobasal degeneration: similarities and differences

Progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD) are sporadic four-repeat tauopathies that have characteristic clinical and neuropathologic profiles, but also share overlapping features. Both present with various clinical phenotypes, but while the clinical diagnostic criteria of the classical and most frequent presentation of PSP have optimal specificity, the diagnostic accuracy of the various CBD phenotypes is suboptimal. On the other hand, neuropathologic diagnostic criteria for PSP and CBD have been validated and have appropriate accuracy. This article discusses the similarities and differences between these two disorders in clinical manifestations, neuroimaging and neuropathology and provides a perspective on possible future developments that may help in their diagnosis and treatment.

Cerebrospinal Fluid Tau Protein Is Increased in Neurosyphilis: A Discrimination From Syphilis Without Nervous System Involvement?

OBJECTIVE

The objective of this study was to investigate the levels of tau protein in neurosyphilis.

STUDY DESIGN

Total tau protein in the cerebrospinal fluid of 12 patients with neurosyphilis, 17 with syphilis without nervous system involvement, 14 controls, and 14 patients with Alzheimer disease of comparable age were analyzed. Double-sandwich enzyme-linked immunosorbent assay was used for measurements.

RESULTS

Increased levels of cerebrospinal fluid total tau were observed in neurosyphilis (median [25th-75th percentile]: 349 pg/mL [312-429]) and in Alzheimer disease (543 [441-1017]) as compared with the controls (189 [106-220]) and syphilis without nervous system involvement (190 [160-223]). Using a cutoff level of 300 pg/mL, increased tau discriminated cases of neurosyphilis from syphilis without nervous system involvement with a sensitivity and specificity of 83% and 94%, respectively.

CONCLUSIONS

These results indicate that increased total tau may be useful in the discrimination of neurosyphilis from syphilis without nervous system involvement.

Cerebrospinal fluid tau, phospho-tau181 and beta-amyloid1-42 in idiopathic normal pressure hydrocephalus: a discrimination from Alzheimer's disease

The aim of the present study was the quantitation of total tau protein (tau(T)), tau phosphorylated at threonine 181 (tau(P-181)) and beta-amyloid(1-42) (Abeta42) in the cerebrospinal fluid (CSF) of patients with idiopathic normal pressure hydrocephalus (iNPH), Alzheimer's disease (AD) and controls. Double sandwich ELISAs (Innogenetics) were used for the measurements. Total tau was significantly increased in iNPH and highly increased in AD as compared with the control group, whilst Abeta42 was decreased in both diseases. CSF tau(P-181) levels were significantly increased only in AD, but not in iNPH as compared with the controls. A cut-off level for tau(T) at 300 pg/ml, successfully discriminated AD from normal aging with a 95.8% specificity and 91% sensitivity; whilst the tau(P-181)/tau(T) ratio (cut-off value 0.169) was more specific (100%) but less sensitive (92.5%). For the discrimination of iNPH from AD tau(T) achieved low specificity (77.8%) but high sensitivity (92.5%), whilst tau(P-181) (cut-off value 47.4) was both sensitive and specific (88.7% and 86.7% respectively) for the discrimination of these disorders. The present study, despite being clinical, supports the notion that CSF tau(P-181) alone or in combination with tau(T) may be a useful marker in the discrimination of iNPH from AD.