Amyloid is a bundle of discarded proteins that when accumulated in the brain may lead to Alzheimer’s disease, a form of dementia. Up until now, the presence of amyloid in the brain was positively identified only by brain biopsy (very impractical) or by detection of amyloid in spinal fluid obtained by spinal tap or by PET scan of the brain (both of which have side effects and are expensive).

Hence, a simple blood test is akin to a breakthrough. The main purpose of trying to detect amyloid is either to diagnose Alzheimer’s disease to allow for a future life planning or to confirm Alzheimer’s disease so that two new drugs, Leqembi and Kisunla, which slow its progression may be prescribed. These two new drugs are extremely expensive, associated with severe side effects and mostly effective in early-stage patients, so their use should not be taken lightly.

The new blood test is similar to the spinal fluid test in that it measures the ratio of brain amyloid to another protein named tau. It is intended for use in adults 50 and over showing memory decline or early dementia symptoms, a major one being inability to make new memories. The blood test itself should not be used alone to diagnose Alzheimer’s as it has both false positives and false negative results. It is best used along with other tests such as neuropsychiatric testing or PET brain scanning.

In summary, it is not useful for the curious patient or the worried well, but it’s best used in those patients with early symptoms, a strong family history of Alzheimer’s or those with what’s known as the apoE4 genotype. A little do-it-yourself test is that if you think you have Alzheimer’s (i.e. you can’t remember where you put your car keys) you probably don’t have it. If your family has noticed changes in your behavior, you are probably a victim.

Dr. Charlie Barnett is a contributor at KnoxTNToday for a weekly column, DocTalk, providing his expertise on health and wellness management.

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