A recent review article in Alzheimer's and Dementia discusses the current state of cerebrospinal fluid-borne markers for Alzheimer disease.2 Tests that identify proteins in the CSF could be very specific to Alzheimer disease because the fluid directly interacts with brain tissue.3 According to first author, Kaj Blennow, MD, PhD, Professor of Clinical Neurochemistry at the Sahlgrenska University Hospital in Mölndal, Sweden, CSF is potentially better than blood since "a brain protein will be diluted in the larger blood volume, metabolized and degraded.
explains "They have been evaluated in hundreds of papers and very consistently show that more than 85%-90% of AD (and prodromal AD) cases have low Abeta42 and high total-tau and phospho-tau."
Levels of CSF amyloid-beta seem to decrease as post-mortem or biopsied brain levels increase, so it seems that the protein may deposit itself in the brain and while it correspondingly decreases in the fluid.
CSF phosphorylated tau levels also correspond with the amount of neurofibrillary tangles found in a later autopsy.
In addition, high levels of total tau in the CSF seem to indicate that mild cognitive impairment will quickly progress to full Alzheimer dementia.
Unfortunately, the markers seem to be only good in the early stages of the disease.
explains: "it seems that the AD biomarkers reach a plateau very early in disease progression, and thus do not change with progression."
Researchers may have another problem with developing a clinical test: the methods being used are not the same in every lab.
The development of consistent assays is a high current priority in this field.
According to Dr Blennow
"what is needed is more work on standardization, both the analytical part and assay production, so that we can get uniform values between labs.