DESCRIPTION
The clinical diagnosis of Alzheimer’s disease (AD) focuses on the exclusion of other causes of dementia. Because diagnosis of AD can be difficult, there has been considerable interest in identifying an accurate laboratory test for AD; particularly for use early in the course of disease. Several cerebrospinal fluid (CSF) peptide markers and urine markers have been investigated as possible predictors of AD.
Tau protein is a microtubule-associated molecule that is found in the neurofibrillary tangles that are typical of AD. This protein is thought to be related to degenerating and dying neurons.
AB-42 is a subtype of amyloid beta peptide that is produced following the metabolism of amyloid precursor protein. AB-42 is the key peptide deposited in the amyloid plaques characteristic of AD.
Low levels of AB-42 in the CSF have been associated with AD.
Neural thread protein is associated with the neurofibrillary tangles of AD. Both CSF and urine levels of this protein have been investigated as a potential marker of AD.
POLICY
Measurement of cerebrospinal fluid biomarkers of Alzheimer’s disease, including but not limited to tau protein, amyloid beta peptides, or neural thread proteins, is considered investigational.
Measurement of urinary biomarkers of Alzheimer’s disease including, but not limited to, neural thread proteins is considered investigational.
Policies with similar titles: Genetic Testing for Alzheimer's Disease
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ADDITIONAL INFORMATION
Evidence that testing for AD-related biomarkers can improve health outcomes is lacking. For the diagnosis of AD, evidence does not demonstrate incremental improvement in diagnostic accuracy as a result of biomarker testing when compared to a clinical diagnosis. For predicting conversion from mild cognitive impairment (MCI) to AD, limited evidence suggests biomarker testing might define increased risk. Whether earlier diagnosis leads to improved health outcomes through delay of AD onset or quality of life is lacking.
The National Institute on Aging and the Alzheimer’s Association conducted a series of advisory meetings in 2009 to establish a process for revising diagnostic and research criteria. There was broad consensus by the working groups that much additional work is needed to validate the application of biomarkers to the diagnostic purpose.
SOURCES
BlueCross BlueShield Association. Medical Policy Reference Manual. (5:2011). Biochemical markers of Alzheimer’s disease (2.04.14). Retrieved July 12, 2011 from BlueWeb. (38 articles and/or guidelines reviewed)
Forlenza, O., Diniz, B., & Gattaz, W. (2010). Diagnosis and biomarkers of predementia in Alzheimer’s disease. BioMed Central Medicine, 8 (89).
Jack, C., Albert, M., Knopman, G., Sperling, R., Carrillo, M., Thies, B. et al. (2011). Introduction to the recommendations from the National Institute on Aging and the Alzheimer’s Association workgroup on diagnostic guidelines for Alzheimer’s disease. Alzheimer’s and Dementia: The Journal of the Alzheimer’s Association, 7 (3), 257-262.
Knopman, D., DeKosky, S., Cummings, J., Chui, H., Corey-Bloom, J., Relkin, N. et al. (2001). Practice parameter: Diagnosis of dementia (an evidence-based review). Report of the quality standards subcommittee of the American Academy of Neurology. Neurology, 56 (9), 1143-1153. (Level 1 Evidence - Independent)
McKhann, G., Knopman, D., Chertkow, H., Hyman, B., Jack, C., Kawas,C., et al. (2011), The diagnosis of dementia due to Alzheimer’s disease: Recommendations from the National Institute on Aging and the Alzheimer’s Association workgroup. Alzheimer’s and Dementia: The Journal of the Alzheimer’s Association, 7 (3), 263-269.
Perrin, R., Craig-Shapiro, R., Malone, J., Shah, A., Gilmore, P., Davis, A., et al. (2011), Identification and validation of novel cerebrospinal fluid biomarkers for staging early Alzheimer's disease. PLoS One, 6 (1). (Level 4 Evidence – Industry sponsored)
Third Canadian Consensus Conference on Diagnosis and Treatment of Dementia. (2007) Retrieved July 12, 2011 from http://www.cccdtd.ca/pdfs/Final_Recommendations_CCCDTD_2007.pdf.
ORIGINAL EFFECTIVE DATE: 12/10/2011
MOST RECENT REVIEW DATE: 12/10/2011
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