Discovery and verification of amyotrophic lateral sclerosis biomarkers by proteomics

Recent studies using mass spectrometry have discovered candidate biomarkers for amyotrophic lateral sclerosis (ALS). However, those studies utilized small numbers of ALS and control subjects. Additional studies using larger subject cohorts are required to verify these candidate biomarkers. Cerebrospinal fluid (CSF) samples from 100 patients with ALS, 100 disease control, and 41 healthy control subjects were examined by mass spectrometry. Sixty‐one mass spectral peaks exhibited altered levels between ALS and controls. Mass peaks for cystatin C and transthyretin were reduced in ALS, whereas mass peaks for posttranslational modified transthyretin and C‐reactive protein (CRP) were increased. CRP levels were 5.84 ± 1.01 ng/ml for controls and 11.24 ± 1.52 ng/ml for ALS subjects, as determined by enzyme‐linked immunoassay. This study verified prior mass spectrometry results for cystatin C and transthyretin in ALS. CRP levels were increased in the CSF of ALS patients, and cystatin C level correlated with survival in patients with limb‐onset disease. Our biomarker panel predicted ALS with an overall accuracy of 82%. Muscle Nerve 42: 104–111, 2010     

Combined proteomic approach with SELDI-TOF-MS and peptide mass fingerprinting identified the rapid increase of monomeric transthyretin in rat cerebrospinal fluid after transient focal cerebral ischemia

Several proteins are known to be markedly expressed in the brain during cerebral ischemia, however the change in protein profiles within the cerebrospinal fluid (CSF) after an ischemic insult has not been fully elucidated. We studied the changes in the CSF proteome in rat transient middle cerebral artery occlusion model. Surface enhanced laser desorption/ionization time-of-flight (SELDI-TOF) mass spectrometry (MS) was used to detect the time-course changes in CSF protein patterns after transient focal brain ischemia. According to hierarchical cluster analysis by self-organising tree algorism (SOTA), the temporal pattern of protein peaks was divided into four groups: acute increase group, chronic increase group, gradual decrease group and unchanged group. In the acute increase group, the expression of a 13.6-kDa protein was markedly increased during the acute phase. The 13.6-kDa protein was identified as monomeric form of transthyretin using two-dimensional electrophoresis and peptide mass fingerprinting based on matrix-assisted laser desorption/ionization-time of flight mass spectrometry. The monomeric transthyretin may represent an ischemia-specific CSF marker to indicate the sequential changes according to ischemic insults of the brain.     

Use of surface enhanced laser desorption/ionization-time of flight mass spectrometry (SELDI-TOF MS) to study protein expression in a rat model of cocaine withdrawal

Surface enhanced laser desorption/ionization-time of flight mass spectrometry (SELDI-TOF MS) is an analytical technology for proteomic analysis that combines chromatography and mass spectrometry. At present, this technology is most commonly being exploited for the simultaneous measurement of numerous proteins in serum, but has also been utilized in organ tissue, although rarely in the brain. We applied SELDI-TOF MS technology to study protein expression in the brain of rats withdrawn from repeated cocaine exposure. Our goals were to optimize sample preparation and ProteinChip Array protocols for brain tissue, to verify the reproducibility of SELDI-TOF mass spectra and to determine whether SELDI-TOF MS detects differentially expressed proteins in cocaine- versus saline-treated rats. Consequently, we have developed an optimal protocol and generated a reproducible spectral pattern with six dominant peaks in all test samples. We have detected two smaller peaks (m/z: 5179, 5030) that were significantly increased (p < 0.05) in cocaine-treated rats compared to saline-treated rats. In summary, the application of SELDI-TOF MS to the study of protein expression in a rat model of cocaine withdrawal is feasible and has the potential to generate new hypotheses.     

Validation of amyloid-beta peptides in CSF diagnosis of neurodegenerative dementias

Biomarkers for differential diagnosis of the three most frequent degenerative forms of dementia, Alzheimer's disease (AD), dementia with Lewy bodies (DLB) and frontotemporal dementias (FTD), are currently under intensive investigation, but disease-specific biomarkers for FTD and DLB are still lacking. We analyzed 303 cerebrospinal fluid (CSF) samples of 71 AD, 32 DLB and 36 FTD patients in comparison to 93 various other dementias (OD), 20 peripheral neurologic disease (PND) controls, 25 neurodegenerative disorders without dementia (ND) and 26 depressive cognitive complainers (DCC) for distinct CSF amyloid-beta (Abeta) peptide patterns, using the quantitative Abeta-SDS-PAGE/immunoblot. Additionally, the novel electrochemiluminescence technique (MSD) was used to validate the measures on Abeta1-38. The main outcome measures were a striking decrease of Abeta1-42 in AD (P=7.4 x 10(-19)), and most interestingly a pronounced decrease of Abeta1-38 in FTD (P=9.6 x 10(-7)). Moreover, a novel peptide that most probably represents an oxidized alpha-helical form of Abeta1-40 (Abeta1-40(ox)) displayed a highly significant increase in DLB (P=3.7 x 10(-3)) as compared to non-demented disease controls. The overall diagnostic accuracy of percentage Abeta peptide abundances (Abeta1-X%) was clearly superior to absolute CSF Abeta levels. Abeta1-42% and Abeta1-38% enabled contrasts of 85% or beyond to distinguish AD and FTD, respectively, from all other investigated subjects. Abeta1-40(ox)% yielded a diagnostic sensitivity and specificity of 88 and 73% for the detection of DLB among all other investigated patients. We found a strong correlation between Abeta1-38 levels as measured by the Abeta-SDS-PAGE/immunoblot and MSD, respectively. CSF Abeta peptides may reflect disease-specific impact of distinct neurodegenerative processes on Abeta peptide metabolism and represent a potential diagnostic biomarker for AD, FTD and DLB.     

Serum proteomic profiling of dementia with Lewy bodies: diagnostic potential of SELDI-TOF MS analysis

Summary Dementia with Lewy bodies (DLB) is the second most common senile degenerative dementia after Alzheimer’s disease (AD). The presentation of overlapping symptoms between these two disorders leads to difficulties in the determination of clinical entities. Serum samples were subjected to surface-enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF MS) analysis in order to identify a diagnostic marker for DLB. Four putative protein peaks (m/z 3,883, 4,964, 7,761 and 10,534) were differentially expressed in DLB patients compared to AD patients and control subjects. Receiver operating characteristics (ROC) analysis of a multivariate logistic model of the combination of three peaks (m/z 3,883, 7,761 and 10,534) exhibited the highest discriminatory ability of DLB subjects from non-DLB subjects with a sensitivity of 83.3%, a specificity of 95.8%, a positive predictive value of 90.9% and a negative predictive value of 92.0%. SELDI-TOF MS profiling, therefore, has revealed a serum signature with high diagnostic potential for DLB.     

Variability in blood-based amyloid-beta assays: the need for consensus on pre-analytical processing

The objective of this study was to examine the diagnostic accuracy of imaging and CSF biomarkers in clinically ambiguous dementia (CAD). 69 patients were prospectively followed. The endpoint was clinical diagnosis at follow-up of 24 months based upon existing criteria. Medial temporal lobe atrophy score on MRI, distinctive patterns on 99 mTc-HMPAO-SPECT, and CSF levels of amyloid-β peptide, total tau protein, and P-tau181P were used together with neuropsychological testing to assess Se (sensitivity) and Sp (specificity) of separate and combined markers. 60 patients reached the endpoint. A definite diagnosis was achieved in 48 patients. CSF biomarkers had a Sp of 71% and a Se of 100% for Alzheimer's disease (AD) diagnosis. Sp increased to 88% and 93% when MRI and MRI + SPECT were combined, at the expense of Se. CSF biomarkers levels also provided clues to frontotemporal (FTD) or vascular dementias (VaD) diagnosis when situated in an intermediate range between normal and pathological values. MRI and SPECT contributed mostly to the diagnosis of VaD (Se 88%, Sp 75%) and FTD (Se 73%, Sp 78%), respectively. Initial neuropsychological testing had a poor diagnostic accuracy, except for a neuropsychiatric inventory score >40 for the diagnosis of FTD (Se 73%, Sp 84%). Independent of the clinical diagnosis, medial temporal lobe atrophy and total-tau were best correlated with cognitive decline at 2 years. In conclusion, CSF biomarkers efficiently predict evolution toward an AD phenotype in CAD. Imaging biomarkers mostly contribute to the differential diagnosis between non-AD dementias. Initial neuropsychological testing was poorly contributive in CAD diagnosis.     

Cerebrospinal fluid amyloid-β 2-42 is decreased in Alzheimer’s, but not in frontotemporal dementia

Alzheimer's dementia (AD) and frontotemporal dementias (FTD) are common and their clinical differential diagnosis may be complicated by overlapping symptoms, which is why biomarkers may have an important role to play. Cerebrospinal fluids (CSF) Aβ2-42 and 1-42 have been shown to be similarly decreased in AD, but 1-42 did not display sufficient specificity for exclusion of other dementias from AD. The objective of the present study was to clarify the diagnostic value of Aβ2-42 peptides for the differential diagnosis of AD from FTD. For this purpose, 20 non-demented disease controls (NDC), 22 patients with AD and 17 with FTD were comparatively analysed by a novel sequential aminoterminally and carboxyterminally specific immunoprecipitation protocol with subsequent Aβ-SDS-PAGE/immunoblot, allowing the quantification of peptides 1-38(ox), 2-40 and 2-42 along with Aβ 1-37, 1-38, 1-39, 1-40, 1-40(ox) and 1-42. CSF Aβ1-42 was decreased in AD as compared to NDC, but not to FTD. In a subgroup of the patients analyzed, the decrease of Abeta2-42 in AD was evident as compared to both NDC and FTD. Aβ1-38 was decreased in FTD as compared to NDC and AD. For differentiating AD from FTD, Aβ1-42 demonstrated sufficient diagnostic accuracies only when combined with Aβ1-38. Aβ2-42 yielded diagnostic accuracies of over 85?% as a single marker. These accuracy figures could be improved by combining Aβ2-42 to Aβ1-38. Aβ2-42 seems to be a promising biomarker for differentiating AD from other degenerative dementias, such as FTD.     

CSF neurofilaments in frontotemporal dementia compared with early onset Alzheimer's disease and controls

BACKGROUND: Frontotemporal dementia (FTD) is pathologically heterogeneous, sometimes revealing intraneuronal inclusions of neurofilaments. We therefore measured CSF neurofilament profiles in patients with FTD, patients with early onset Alzheimer's disease (EAD) and healthy control subjects to explore the discriminative potential of CSF neurofilaments compared with the existing CSF biomarkers amyloid-beta(1-42), tau and tau phosphorylated at threonine-181. METHODS: CSF levels of light chain, heavy chain and hyperphosphorylated heavy chain neurofilaments (NfL, t-NfH and P-NfH) were compared between 17 subjects with FTD, 20 with EAD and 25 cognitively healthy controls. RESULTS: A subgroup of FTD patients had remarkably high CSF levels of both NfL and NfH. The degree of NfH phosphorylation was increased in FTD compared to both other groups. The levels of CSF NfL were significantly higher in EAD compared to controls. CONCLUSION: Differences in CSF biomarker profiles might reflect differential involvement of neurofilaments and tau in FTD and EAD. The subgroup of FTD patients with high CSF neurofilament levels may have a different neuropathological substrate and future studies addressing this specific issue are needed.     

应用DIGE测定帕金森病脑脊液中蛋白变化

目的 测定帕金森病(PD)脑脊液中蛋白的变化,为进一步探索PD的生物标记物提供线索.方法 采用荧光差异凝胶电泳技术分离并筛选PD和正常对照者脑脊液中差异表达蛋白质,用基质辅助激光解吸电离飞行时间质谱(MALDI-TOF MS)或串联质谱技术进行鉴定并分析.结果 共发现20个明显的差异蛋白点,其中11个点在PD中上调,9个点下调.共鉴定出8个蛋白质,其中有3个未知蛋白,均表现为下调.蛋白MYPT1出现明显下调,载脂蛋白原、脂蛋白发生明显上调,载脂蛋白A-I的一个异构体发生上调,一个异构体发生下调.结论 MYPT1与突触功能有关,载脂蛋白原、脂蛋白、载脂蛋白A-I与胆固醇代谢有关,这些蛋白与PD发生有一定关联,有可能成为PD的生物标记物.     

Decreased serum levels of nucleolin protein fragment, as analyzed by bead-based proteomic technology, in multiple sclerosis patients compared to controls

In order to investigate the biomarkers associated with relapsing-remitting multiple sclerosis (RRMS), we analyzed 72 patients with RRMS and 65 healthy controls using proteome technology. Peptides in sera were purified using magnetic beads, and analyzed by matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry and ClinProTool software. Thirteen peptides were significantly different between patients with RRMS and healthy controls. Furthermore, a pattern of peaks was selected for genetic algorithm (GA), supervised neural network (SNN) and quick classifier (QC) model building. Among these three models, GA method was best with 93.49% of recognition capability and 82.66% of cross-validation and discriminated the proteomic spectra in patients with RRMS from healthy controls, with a sensitivity of 80% and a specificity of 91.3%. Meanwhile, the first peptide with m/z 2023.3 was identified as fragment of nucleolin protein. There is a possible relationship between the fragment peptide of nucleolin and the trigger of relapse in MS. Sera nucleolin may serve as a possible biomarker of RRMS.     

Clinic-based cases with frontotemporal dementia show increased cerebrospinal fluid tau and high apolipoprotein E epsilon4 frequency, but no tau gene mutations

Frontotemporal dementia (FTD) belongs to a group of neurodegenerative disorders known as tauopathies, characterized by intracellular aggregation of hyperphosphorylated tau protein in the brain. Some tauopathies, like Alzheimer's disease (AD), consistently show increased levels of tau protein in cerebrospinal fluid (CSF). However, similar studies in FTD populations have shown variable results, although mutations in the tau gene are identified as causes of disease in certain FTD families. In the present study, a Swedish clinic-based FTD population was investigated with respect to CSF tau levels, apolipoprotein E (APOE) genotype distribution and occurrence of mutations in the tau gene. CSF tau levels were significantly increased among FTD patients (534 +/- 235 pg tau/ml, P < 0.001) (n = 47) compared to controls (316 +/- 137 pg tau/ml) (n = 51). Furthermore, a strong increase in the APOE epsilon4 allele frequency was found in the FTD population, as 52% were epsilon4 carriers, compared to 21% of the controls. However, no mutations in the tau gene were identified. These findings support the present notion of a common pathogenic pathway in the disease processes for several tauopathies, with both APOE epsilon4 and CSF tau being a pathological link between the different disorders. Furthermore, we conclude that mutations in the tau gene are a rare cause of FTD. .     

Studies of the pathophysiological mechanisms in frontotemporal dementia by proteome analysis of CSF proteins

Comparative proteomic analysis of cerebrospinal fluid (CSF) proteins was employed for studies of the pathophysiological mechanisms in frontotemporal dementia (FTD). Two-dimensional gel electrophoresis and mass spectrometry were used for clinical screening of disease-influenced CSF proteins in 15 FTD patients compared to 12 controls. Six proteins were significantly altered in FTD compared to controls, including granin-like neuroendocrine precursor (proSAAS), pigment-epithelium derived factor (PEDF), retinol-binding protein (RBP), apoE, haptoglobin, and albumin. The levels of ProSAAS, PEDF, and RBP have not been shown earlier to be involved in the FTD pathology. Recently, we have also used proteomic analysis for studies of disease-influenced CSF proteins in Alzheimer's disease (AD) patients. The most clearly affected CSF proteins were the apolipoproteins in AD, compared to controls and FTD patients. ApoE seems to be influenced to a lesser degree in FTD compared to AD. Our data showed that several proteins involved in FTD pathology are not influenced in the CSF of AD patients, and vice versa, establishing differences in the pathophysiological mechanisms between FTD and AD, two of the most common neurodegenerative disorders.     

Clinic-Based Cases with Frontotemporal Dementia Show Increased Cerebrospinal Fluid Tau and High Apolipoprotein E 4 Frequency, but No Tau Gene Mutations

Frontotemporal dementia (FTD) belongs to a group of neurodegenerative disorders known as tauopathies, characterized by intracellular aggregation of hyperphosphorylated tau protein in the brain. Some tauopathies, like Alzheimer's disease (AD), consistently show increased levels of tau protein in cerebrospinal fluid (CSF). However, similar studies in FTD populations have shown variable results, although mutations in the tau gene are identified as causes of disease in certain FTD families. In the present study, a Swedish clinic-based FTD population was investigated with respect to CSF tau levels, apolipoprotein E (APOE) genotype distribution and occurrence of mutations in the tau gene. CSF tau levels were significantly increased among FTD patients (534 ± 235 pg tau/ml, P < 0.001) (n = 47) compared to controls (316 ± 137 pg tau/ml) (n = 51). Furthermore, a strong increase in the APOE 4 allele frequency was found in the FTD population, as 52% were 4 carriers, compared to 21% of the controls. However, no mutations in the tau gene were identified. These findings support the present notion of a common pathogenic pathway in the disease processes for several tauopathies, with both APOE 4 and CSF tau being a pathological link between the different disorders. Furthermore, we conclude that mutations in the tau gene are a rare cause of FTD.     

Variant transthyretin in cerebrospinal fluid in familial amyloidotic polyneuropathy

Structurally abnormal transthyretin is a precursor protein of amyloid fibrils in type I familial amyloidotic polyneuropathy (FAP). This variant transthyretin has an amino acid substitution of methionine for valine at position 30. The purpose of this study was to clarify whether this variant transthyretin also circulates in the cerebrospinal fluid (CSF) of patients with type I FAP. CSF transthyretin of the patients was purified and its primary structure determined. Sequence determination indicated that transthyretin consisted of a mixture of normal and variant transthyretin. Variant transthyretin was present in the CSF of all 5 Japanese FAP patients studied. The CSF concentration of variant transthyretin was high (0.72 +/- 0.15 mg/dl, mean +/- S.D.), suggesting that variant transthyretin is synthesized in the choroid plexus. Variant transthyretin was not present in any of 20 controls. The CSF concentration of total transthyretin in FAP patients was 1.74 +/- 0.42 mg/dl, which was not significantly different from controls.     

A single center study: Aβ42/p-Tau<Subscript>181</Subscript> CSF ratio to discriminate AD from FTD in clinical setting

Abnormal levels of beta amyloid (Aβ42) and tau protein concentrations in the cerebral spinal fluid (CSF) have been largely described in Alzheimer’s disease (AD). Thus, CSF analysis of these biomarkers has been incorporated in recent AD diagnostic criteria, and it is increasingly performed for neurodegenerative dementia diagnostic workout in clinical setting. Nevertheless, the precise biomarkers CSF features in neurodegenerative dementia, either AD or Frontotemporal dementia (FTD), are still not fully clear today. This is mainly due to lack of CSF clear cutoff values due to a well-known intersite (but even intrasite) variability of CSF procedures, ranging from collection to analysis. Applying CSF biomarker ratios, rather than their single values could represent a useful tool, especially for the differential diagnosis of different forms of dementia. We explored clinical values of six CSF ratios (by combining Aβ42 and tau) in order to better discriminate between AD and FTD; we identified Aβ42/p-Tau₁₈₁ ratio as a potential good candidate for helping differentiating AD from FTD in the clinical practice.     

Cerebrospinal-fluid orexin levels and daytime somnolence in frontotemporal dementia

Daytime somnolence and sleep–wake cycle disturbances are commonly encountered symptoms in Frontotemporal Dementia (FTD). Orexin-A (Hypocretin-1) is a hypothalamic neuropeptide regulating the sleep–wake rhythm. We investigated the cerebrospinal-fluid (CSF) orexin levels in a population of FTD patients and evaluated whether there is a relationship between daytime somnolence and CSF orexin concentrations. CSF orexin levels were measured in a sample of FTD patients (n = 11) compared to a population of non-demented controls (n = 13) similar for age and sex. Moreover, CSF orexin concentrations were correlated with daytime somnolence investigated by means of the Epworth Sleepiness Scale (ESS) in both FTD patients and controls. FTD patients showed CSF orexin concentrations (164.3 ± 66.45 vs 170.81 ± 42.73 pg/mL) and ESS scores (7.45 ± 4.36 vs 3.84 ± 1.82) not different from controls. However, three FTD patients showed pathological daytime sleepiness (ESS > 10) coupled with the lowest CSF orexin levels. In addition, we found a significant negative correlation between CSF orexin levels and ESS scores in the FTD population (R = ?0.91; p < 0.0001), which was not evident in the control group (R = 0.16; p > 0.05). This is the first study investigating CSF orexin concentrations in FTD. We did not find differences in CSF orexin concentrations between FTD patients and controls. However, a significant negative correlation between daytime somnolence and CSF orexin levels was evident in FTD patients. Moreover, we have found that pathological daytime somnolence was evident in those FTD patients with the lowest CSF orexin levels. Based on these findings, we argued that lower orexin levels may be permissive for increased daytime somnolence in FTD.     

Tau and Abeta42 protein in CSF of patients with frontotemporal degeneration

BACKGROUND: CSF concentrations of tau and beta-amyloid protein-42 (Abeta42) have been extensively studied in AD. Few data are available concerning CSF levels of both proteins in patients with frontotemporal degeneration (FTD). METHODS: The authors investigated CSF tau and Abeta42 concentrations in 34 patients with FTD, 74 patients with AD, and 40 cognitively healthy control subjects. CSF levels of tau and Abeta42 were measured by ELISA. With use of receiver operating characteristic-derived cutoff points and linear discrimination lines, the diagnostic sensitivity and specificity of both markers were determined. RESULTS: CSF tau concentrations were significantly higher in FTD than in control subjects but were significantly lower than in AD. CSF Abeta42 levels were significantly lower in FTD than in control subjects but were significantly higher than in AD. In subjects with FTD, neither tau nor Abeta42 levels correlated with the severity of dementia. The best discrimination between the diagnostic groups was obtained by simultaneous measurement of tau and Abeta42, yielding a sensitivity of 90% at a specificity of 77% (FTD vs controls) and a sensitivity of 85% at a specificity of 85% (FTD vs AD). CONCLUSIONS: In FTD, CSF levels of tau are elevated and Abeta42 levels are decreased. With use of these markers, subjects with FTD can be distinguished from control subjects and from patients with AD with reasonable accuracy.     

A new procedure for detecting brain-specific proteins in cerebrospinal fluid

Summary We have developed a new procedure, including three affinity chromatography steps, micro-reversed phase high pressure liquid chromatography (mR-HPLC) and Western blotting/mass spectrometric analysis to study central nervous system (CNS) specific proteins in human cerebrospinal fluid (CSF) in order to find biochemical markers for neuronal and synaptic function and pathology in degenerative brain disorders. After the three affinity chromatography steps, intended to remove interfering serum proteins from CSF, mR-HPLC revealed four major peaks, which by both Western blotting and mass spectrometric analyses were found to correspond to 2-microglobulin, cystatin C, transthyretin (TTR) and asialotransferrin. When comparing these peaks in CSF from Alzheimer's disease (AD) patients and age-matched healthy controls, a reduction of the brain-specific TTR was found. Therefore we quantified TTR in CSF and serum samples from 8 patients with early onset AD (EAD), 18 patients with late onset AD (LAD), 8 patients with vascular dementia (VAD) and 18 healthy individuals using a nephelometric method. CSF-TTR was divided into barrier-dependent and barrier-independent TTR. The barrier-independent i.e. brain-specific TTR was significantly reduced in the EAD group compared to the controls. Transthyretin has been found to be present in the senile plaques in AD, and to specifically bind to /A4 protein, the major component of the amyloid deposits in AD. Therefore, the reduction of the transthyretin-isoform in CSF in AD may reflect an absorption of transthyretin to the amyloid deposits in the senile plaques.     

Quantitative analysis of transthyretin, tau and amyloid-beta in patients with dementia

We carried out a quantitative analysis of transthyretin (TTR), total tau protein and amyloid-beta (Abeta) peptide (1-40 and 1-42) in the lumbar cerebrospinal fluid of 106 patients with different forms of dementia including Alzheimer's disease (AD), Creutzfeldt-Jakob-disease (CJD), dementia with Lewy bodies (DLB), frontotemporal dementia (FTD) and normal pressure hydrocephalus (NPH) in comparison to healthy controls. Our study revealed that Abeta_{1-42} levels were decreased in all patients irrespective of dementia type. Tau protein levels were abnormal in all degenerative dementia except of NPH. Tau levels did not allow differential diagnosis of dementia type except for CJD, where we observed extremely high CSF levels. In other dementia types, levels were elevated in a similar range. Transthyretin levels were selectively decreased in AD and NPH, thus revealing the potential of this protein to be used as additional biomarker in the neurochemical differential diagnosis of AD. A significant negative correlation of TTR CSF levels and disease severity in AD was observed.     

Differential diagnosis of Alzheimer disease with cerebrospinal fluid levels of tau protein phosphorylated at threonine 231

BACKGROUND: Phosphorylation of tau protein at threonine 231 (using full-length tau, 441 amino acids, for the numbering scheme) (p-tau(231)) occurs specifically in postmortem brain tissue of patients with Alzheimer disease (AD) and can be sensitively detected in cerebrospinal fluid (CSF). OBJECTIVES: To determine to what extent CSF levels of p-tau(231) distinguish patients with AD from control subjects and from patients with other dementias, and to investigate whether p-tau(231) levels are a better diagnostic marker than levels of total tau protein (t-tau) in CSF. DESIGN AND SETTING: Cross-sectional, multicenter, memory clinic-based studies. PARTICIPANTS: One hundred ninety-two patients with a clinical diagnosis of AD, frontotemporal dementia (FTD), vascular dementia, Lewy body dementia, or other neurological disorder and healthy controls. MAIN OUTCOME MEASURES: Levels of CSF tau proteins as measured with enzyme-linked immunosorbent assays. RESULTS: Mean CSF levels of p-tau(231) were significantly elevated in the AD group compared with all other groups. Levels of p-tau(231) did not correlate with dementia severity in AD, and discriminated with a sensitivity of 90.2% and a specificity of 80.0% between AD and all non-AD disorders. Moreover, p-tau(231) levels improved diagnostic accuracy compared with t-tau levels when patients with AD were compared with healthy controls (P =.03) and demented subjects (P<.001), particularly those with FTD (P<.001), but not those with vascular and Lewy body dementias. Sensitivity levels between AD and FTD were raised by p-tau(231) compared with t-tau levels from 57.7% to 90.2% at a specificity level of 92.3% for both markers. CONCLUSION: Increased levels of CSF p-tau(231) may be a useful, clinically applicable biological marker for the differential diagnosis of AD, particularly for distinguishing AD from FTD.