Study: Spinal Chemicals May Help in Diagnosis of Alzheimer's Disease

Measuring two specific chemicals contained in spinal fluid may help doctors accurately diagnose Alzheimer's disease, according to a study reported in the September issue of the Archives of Neurology.

The current process used to diagnose Alzheimer disease is both time-consuming and costly, depending primarily on the judgment of physicians and requiring neurological examinations, neuropsychological testing, neuroimaging and blood tests. However, the accuracy rate in diagnosing this disease is still only 80 to 90 percent.

Realizing that biochemical tests could direct physicians rapidly to the correct diagnosis, a team of Swiss researchers measured the amount of two chemicals known as phosphorylated tau protein and beta-amyloid peptide42 in the spinal fluid of 100 patients referred to a specialty dementia clinic and 31 healthy patients who served as controls.

The researchers found that that the ratio of the two spinal fluid chemicals was significantly increased in patients with Alzheimer's disease enabling them to accurately distinguish patients with Alzheimer's disease from healthy control subjects.

"We found that calculation of the ratio of phosphorylated tau protein to beta-amyloid peptide42 resulted in high diagnostic accuracy and may, therefore, constitute a diagnostic tool that is suitable for routine clinical use," concluded the researchers.

However, the researchers said it is probably unrealistic to expect diagnostic accuracy levels above 90 percent by measuring amyloid peptides and tau proteins alone since a variety of additional lesions, such as infarcts, gliosis, argyrophilic grains and Lewy bodies, are evident in the brains of Alzheimer's patients analyzed after their deaths.

"In the future, a biochemical marker pattern reflecting the whole spectrum of abnormal proteins deposited in the brain will most likely provide a more accurate diagnosis of Alzheimer's disease, comparable with the current criteria for the neuropathological classification," added the researchers.

Other sources: Archives of Neurology 2003;60:1202-1206