Working Towards an Earlier Diagnosis of Alzheimer’s
Tue, August 24, 2010 at 02:00AM More and more lab or imaging methods are being reported that are intended to help make a diagnosis of Alzheimer’s disease as early as possible. One can argue if that is really desirable, given that there are no treatments that appear to be able to curtain the condition; however, there are some behavioral modifications that may help, and an early certain diagnosis might serve as a stimulus for making family and/or business decisions. Protein patterns in the cerebrospinal fluid represent one of the most recently reported tests; the results are described in an article in the Archives of Neurology.
Alzheimer’s disease is characterized by the presences of plaques of amyloid material and tangles of neurons formed from tau proteins in the brain tissue at autopsy. Researchers measured the spinal fluid concentrations of beta-amyloid protein 1-42 and phosphorylated tau (181P) protein in cognitively normal people, patients with Alzheimer’s, and people with mild cognitive impairment.
It was found that there was a "signature" pattern of low beta-amyloid levels and increased phosphorylated tau in Alzheimer patients. The pattern was found in 90% of such patients, 72% of individuals with mild cognitive impairment, and 36% of the cognitively normal. The researchers concluded that Alzheimer’s manifests itself earlier than previously believed and that the current diagnostic criteria for the disease should be revised.
It’s difficult to see how this test would (or could) be used in clinical practice. What is one to make of a positive result in someone with normal cognition? Are they ‘on the path’ towards developing cognitive impairment and subsequent dementia? Or do they just represent the lack of specificity of a diagnostic test?
Anyhow, not many patients will submit to a spinal tap unless the result is likely to provide specifically useful information. It’s not a procedure that can be done readily in your doctor’s office, and testing the fluid obtained will likely be expensive . . .
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