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Behavior of biomarkers in CSF: Differential Diagnosis of Dementia by ELISA

Posted in Alzheimer's Disease, Etiology, tagged AD, alzheimer's, Alzheimers Disease, Beta amyloid, cerebrospinal fluid, cohort study, dementia, differential diagnosis, Dr. Venkat S. Karra, ELISA, Frontotemporal lobar degeneration, Innogenetics, MCI, Mild cognitive impairment, Tau protein on July 19, 2012| 2 Comments »

Curated by: Dr. Venkat S. Karra, Ph.D.

The number of patients with dementia have been increasing exponentially with the aging of society. The development of AD research has clarified that the pathogenesis of AD is initiated by Aβ amyloidosis with secondary tauopathy and provided a strategy for investigating drugs that may improve or cure AD.

Mild cognitive impairment (MCI) as a prodromal stage of AD and the pathogenesis of Dementia with Lewy bodies (DLB) and Frontotemporal lobar degeneration (FTLD) as a non-AD type dementia have also been elucidated. Currently, a consortium study by the Alzheimer Disease Neuroimaging initiative (ADNI) is being performed to establish global clinical evidence regarding a neuropsychiatric test battery, CSF biomarkers, neuroimaging including MRI, FDG-PET, and amyloid PET to predict progression from MCI to AD and to promote studies of basic therapy for AD [1].

Several new biomarkers such as Aβ oligomer, α-synuclein, and TDP-43 are now under investigation for further determination of their usefulness to detect AD and other non-AD type dementia.

Cerebrospinal Fluid Aβ40, Aβ42, Tau, and Phosphorylated Tau biomarkers have been used for a clinical diagnosis of AD, discrimination from the Vascular dementia (VaD) and non-AD type dementia, exclusion of treatable dementia and MCI, prediction of AD onset and evaluation of the clinical trials of an anti-Aβ antibody, Aβ vaccine therapy, and secretase inhibitors [2–4].

In the current study Schoonenboom et al., [10] conducted a large cohort of patients with different types of dementia to determine how amyloid β 42 (Aβ42), total tau (t-tau), and phosphorylated tau (p-tau) levels behave in CSF.

Aβ is produced mainly in the nerve cells of the brain, and it is secreted about 12 hours later into the CSF, then excreted through the blood-brain barrier 24 hours later into blood (Aβ clearance), and finally degraded in the reticuloendothelial system. Aβ levels are regulated in strict equilibrium among the brain, CSF, and blood [6, 7]. Aβ levels are high while awake and low while a sleep suggesting the presence of a daily change in the CSF Aβ amounts and it is because Aβ amounts in CSF are controlled by orexin and thus collection of CSF by lumbar puncture early in morning in a fasting state is recommended [5].

In AD brains, Aβ42 forms insoluble amyloids and accumulates as insoluble amyloid fibrils in the brain. The reason Aβ42 levels are decreased in the CSF of AD patients is considered to be caused by deterioration of physiologic Aβ clearance into the CSF in AD brains [2, 3]. CSF total tau levels increase slightly with aging. However, CSF tau levels show a 3-fold greater increase in AD patients than in normal controls [8].

It is thought that the rise in CSF total tau is related to degeneration of axons and neurons and to severe destructive disease of the nervous system. Several diseases show slightly increased tau levels such as VaD, multiple sclerosis, AIDS dementia, head injury, and tauopathy. However, CSF tau levels show significant increases in Creutzfeldt-Jakob disease (CJD) and meningoencephalitis [8].

These biomarkers can be measured with an Amyloid ELISA Kit (Wako), which is commercially available and used worldwide. The ELISA kit was developed in Japan by Suzuki et al. and shows extremely high sensitivity and reproducibility [9]. INNOTEST β-AMYLOID1-42 (Innogenetics), for Aβ42 is used widely in Europe and America.

Several assay kits for total tau and phosphorylated tau are also used for the measurement of CSF tau. Currently, total tau is measured using INNOTEST hTau Ag (Innogenetics). There are 3 ELISA systems for measurement of phosphorylated tau that recognize the special phosphorylation sites at Ser199 (Mitsubishi Chemical Corp.), Thr181 (Innogenetics) and Thr231 (Applied NeuroSolutions Inc.), and phosphorylated tau levels are increased in CSF of AD on assays using these kits. Of these 3 kits, INNOTEST PHOSPHO-TAU (181) (Innogenetics) is commercially available and used widely. Recently, INNO-BIA AlzBio3 by Innogenetics has been able to measure Aβ1-42, total tau, and P-tau181P simultaneously in 75 μL of CSF, which is a very small amount of CSF.

In the current study researchers used the following strategy to collect Baseline CSF and Aβ42, t-tau, and p-tau (at amino acid 181) were measured in CSF by ELISA:

Types of patients with Alzheimer disease (AD) = 512 patients
Types of patients with other types of dementia (OD) = 272 patients
Types of patients with a psychiatric disorder (PSY) = 135 patients
Types of patients with subjective memory complaints (SMC) = 275 patients
Autopsy was obtained in a subgroup of about 17 patients.

The study suggested that CSF Aβ42, t-tau, and p-tau are useful in differential dementia diagnosis, whereas in DLB, FTLD, VaD, and CBD, a substantial group exhibited a CSF AD biomarker profile, which requires more autopsy confirmation in the future.

The study found a correct classification of patients with AD (92%) and patients with OD (66%) when CSF Aβ42 and p-tau were combined.
Patients with progressive supranuclear palsy had normal CSF biomarker values in 90%.

Patients with Creutzfeldt-Jakob disease demonstrated an extremely high CSF t-tau at a relatively normal CSF p-tau.

CSF AD biomarker profile was seen in

47% of patients with dementia with Lewy bodies (DLB),

38% in corticobasal degeneration (CBD), and

30% in frontotemporal lobar degeneration (FTLD) and vascular dementia (VaD).

PSY and SMC patients had normal CSF biomarkers in 91% and 88%.

Older patients are more likely to have a CSF AD profile.

Concordance between clinical and neuropathologic diagnosis was 85%.

CSF markers reflected neuropathology in 94%.

The study concluded that CSF Aβ42, t-tau, and p-tau are useful in differential dementia diagnosis. However, in DLB, FTLD, VaD, and CBD, a substantial group exhibit a CSF AD biomarker profile, which requires more autopsy confirmation in the future.

References:

1. R. C. Petersen, P. S. Aisen, L. A. Beckett et al., “Alzheimer’s Disease Neuroimaging Initiative (ADNI): clinical characterization,” Neurology, vol. 74, no. 3, pp. 201–209, 2010.

2. M. Shoji and M. Kanai, “Cerebrospinal fluid Aβ40 and Aβ42: natural course and clinical usefulness,” Journal of Alzheimer’s Disease, vol. 3, no. 3, pp. 313–321, 2001.

3. M. Shoji, M. Kanai, E. Matsubara et al., “The levels of cerebrospinal fluid Aβ40 and Aβ42(43) are regulated age-dependently,” Neurobiology of Aging, vol. 22, no. 2, pp. 209–215, 2001.

4. M. Kanai, E. Matsubara, K. Isoe et al., “Longitudinal study of cerebrospinal fluid levels of tau, Aβ1-40, and Aβ1-42(43) in Alzheimer’s disease: a study in Japan,” Annals of Neurology, vol. 44, no. 1, pp. 17–26, 1998.

5. J. E. Kang, M. M. Lim, R. J. Bateman et al., “Amyloid-β dynamics are regulated by orexin and the sleep-wake cycle,” Science, vol. 326, no. 5955, pp. 1005–1007, 2009.

6. M. Shoji, T. E. Golde, J. Ghiso et al., “Production of the Alzheimer amyloid β protein by normal proteolytic processing,” Science, vol. 258, no. 5079, pp. 126–129, 1992.

7. R. J. Bateman, E. R. Siemers, K. G. Mawuenyega et al., “A γ-secretase inhibitor decreases amyloid-β production in the central nervous system,” Annals of Neurology, vol. 66, no. 1, pp. 48–54, 2009.

8. M. Shoji, E. Matsubara, T. Murakami et al., “Cerebrospinal fluid tau in dementia disorders: a large scale multicenter study by a Japanese study group,” Neurobiology of Aging, vol. 23, no. 3, pp. 363–370, 2002.

9. N. Suzuki, T. T. Cheung, X. D. Cai et al., “An increased percentage of long amyloid β protein secreted by familial amyloid β protein precursor (βAPP) mutants,” Science, vol. 264, no. 5163, pp. 1336–1340, 1994.

Source:

10. N.S.M. Schoonenboom et al., Cerebrospinal fluid markers for differential dementia diagnosis in a large memory clinic cohort

For further insight read the following excellent review article by M. Shoji

Biomarkers of Dementia