Experts establish guidelines for assessing Alzheimer's markers
This article was originally published in Clinica
Of the many marker tests for Alzheimer's disease currently available, genetic testing could be one of the best ways of confirming whether somebody has the disease, experts have suggested.
In an eagerly awaited report, the panel of international scientists established new guidelines for assessing both current and future early diagnostic markers for Alzheimer's disease. Sponsored by the Alzheimer's Association's Reagan Research Institute in Chicago and the National Institute on Aging in Maryland, the report stated that an ideal biomarker for the disease should have a sensitivity and specificity greater than 80%. The test should also be reliable, reproducible, non-invasive, simple to perform and inexpensive, it said.
The report, published in the April issue of Neurobiology of Aging, recommended steps to establish a biomarker. These included "confirmation by at least two independent studies conducted by qualified investigators with the results published in peer-reviewed journals."
In its review of current markers, the panel said that for early-onset Alzheimer's disease that runs in families, it would be appropriate to test for mutations in the presenilin 1, presenilin 2 and amyloid precursor protein genes. The experts noted, however, that these mutations were relatively rare and have only been found in 120 families worldwide. Testing should be limited to those with a family history of early-onset Alzheimer's, they said.
The panel said that for late-onset and sporadic Alzheimer's disease, detecting the ApoE4 form of the apolipoprotein E gene could "add confidence to the clinical diagnosis". However, the experts stressed that a test for ApoE4 should not be used as a sole diagnostic test for the disease and it was not appropriate for individuals who have no symptoms of Alzheimer's.
The report found that a number of other tests for the disease do not yet fulfil the recommended criteria for Alzheimer's testing. These included: assays for amyloid deposits in the skin; a test for pupil dilation in response to tropicamide; a cerebrospinal fluid test for neuronal thread proteins and a test for serum levels of iron-binding protein.
However, the panel noted that cerebrospinal fluid tests showing abnormal levels of the proteins amyloid beta-42 and tau, came "closest to fulfilling criteria for a useful biomarker".
US company Athena Diagnostics welcomed the report. The company currently produces tests based on ApoE4, Presenilin 1, tau and amyloid beta-42. Robert Flaherty, Athena's president and CEO said: "We are pleased to see this validation of our testing services."