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Possible Alzheimer's Disease

1. May be made on the basis of the dementia syndrome in the absence of other neurological, psychiatric, or systemic disorders sufficient to cause dementia, and in the presence of variations in the onset, in the presentation, or in the clinical course.
2. May be made in the presence of a second systemic or brain disorder sufficient to produce dementia, which is not considered to be the cause of the dementia.
3. Should be used in research studies when a single gradually progressive severe cognitive deficit is identified in the absence of other identifiable cause.

Probable Alzheimer's Disease

The criteria for the clinical diagnosis of probable AD include:

1. Dementia, established by clinical examination and documented by the Mini-Mental State Examination, the Blessed Dementia Scale, or some similar examination and confirmed by neuropsychological tests.
2. Deficits in two or more areas of cognition
3. Progressive worsening of memory and other cognitive functions
4. No disturbance of consciousness
5. Onset between ages 40 and 90, most often after the age of 65
6. Absence of systemic disorders or other brain diseases that in and of themselves could account for the progressive deficits in memory and cognition.

The diagnosis of probable AD is supported by:

1. Progressive deterioration of specific cognitive functions such as language (aphasia), motor skills (apraxia), and perception (agnosia).
2. Impaired activities of daily living and altered patterns of behavior
3. Family history of similar disorders, particularly if confirmed neuropathologically
4. Laboratory results: normal lumbar puncture as evaluated by standard techniques, normal pattern or non-specific changes in the EEG, and evidence of cerebral atrophy on CT scanning with progression documented by serial observation.

Other clinical features consistent with the diagnosis of probable AD, after exclusion of causes of dementia other than AD, include

1. Plateaus in the course of progression of the illness;
2. Associated symptoms of depression, insomnia, incontinence, delusions, illusions, hallucinations, sexual disorders, weight loss, and catastrophic verbal, emotional, or physical outbursts;
3. Other neurologic abnormalities in some patients, especially with more advanced disease and including motor signs such as increased muscle tone, myoclonus, or gait disorder;
4. Seizures in advanced disease CT normal for age

Features that make the diagnosis of probable AD uncertain or unlikely include;

1. Sudden apoplectic onset
2. Focal neurological findings such as hemiparesis, sensory loss, visual field deficits, and incoordination early in the course of the illness
3. Seizures or gait disturbances at the onset or very early in the course of the illness

Definite Alzheimer's Disease

1. Clinical criteria for probable Alzheimer's disease AND
2. Histopathologic evidence obtained from a biopsy or autopsy

Accompanying advances defining the AD phenotype and pathophysiology “research criteria for the diagnosis of Alzheimer’s disease” have been recently proposed including clinical features, neuroimaging, genetic markers, and biomarkers. However, existing evidence and current practice relies on the NINCDS/ADRDA classifications.

Because diagnosis of AD can be difficult for both physicians, patients, and families there has been considerable interest in identifying an accurate laboratory test for AD - particularly for use early in the course of disease. Abnormal cerebrospinal fluid (CSF) levels of the tau protein (phosphorylated [P-tau] or with a threonine moiety [T-tau]) or an amyloid beta (AB) peptide such as AB-42 have been found in patients with AD. Other potential CSF peptide markers have also been explored. The 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, and high levels of tau proteins in the CSF have been associated with AD. 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, perhaps because AB-42 is deposited in amyloid plaques instead of remaining in solution. Finally, investigators have suggested the Tau/AB-42 ratio a potentially more accurate diagnostic marker than either alone.

Neural thread protein is another protein that is associated with neurofibrillary tangles of Alzheimer's disease. Both CSF and urine levels of this protein have been investigated as a biochemical marker of Alzheimer's disease. Urine and CSF tests for neural thread protein may be referred to as the AD7C^TM test, as developed by Nymox Pharmaceutical Corporation.

Genetic testing for Alzheimer's disease has also been investigated and is considered separately in the Genetic Testing for Familial Alzheimer's Disease medical policy.

Measurement of urinary biomarkers of Alzheimer's disease is considered investigational, including but not limited to neural thread proteins.

None

The coverage guidelines outlined in the Medical Policy Manual should not be used in lieu of the Member's specific benefit plan language.

9/2/2003: Code Reference section completed

12/17/2008: Policy reviewed, no changes

05/13/2010: Policy description updated with new research findings; policy statement unchanged.  Added CPT codes 83520 and 83912, which are used to identify the steps in testing for tau protein and amyloid beta peptides.  There are no specific codes used for testing for neural thread protein.

07/29/2011: Policy reviewed; no changes.

11/28/2012: Policy reviewed; no changes.

Non-Covered Codes

This is not an all-inclusive list of non-covered procedure codes. 

All codes billed for this procedure are considered investigational and not eligible for coverage.