Biomarkers May Aid in Early Diagnosis of Alzheimer's
MONDAY Sept. 13, 2010 -- New research suggests that biomarkers in the blood may help diagnose Alzheimer's disease before it progresses, potentially opening the door to better treatments.
While there are currently no treatments that can halt or delay the onset of the disease, the hope is that being able to diagnose Alzheimer's earlier could provide clues about what medication might prevent it from getting worse, the study authors said.
"Most of the research to this point has been done on those who already have Alzheimer's disease," said study author Sid O'Bryant, director of research for the F. Marie Hall Institute for Rural and Community Health at Texas Tech University Health Sciences Center. "We need to be able to identify those at greatest risk."
In the study, researchers analyzed 100 biomarkers in the blood serum drawn from 197 patients with Alzheimer's and 203 people without Alzheimer's.
Participants were assigned a "risk score" based on levels of the various biomarkers, including C-reactive protein and interleukin-10, which have been associated with inflammation. About 22 of the 100 biomarkers emerged as the most significant, according to the study.
The biomarker risk score accurately identified 80 percent of those who had Alzheimer's disease. When Alzheimer's risk factors, such as age, sex, education and genetic information, were included, the test's accuracy was 94 percent.
Conversely, the biomarker risk score accurately identified who did not have the disease 91 percent of the time. When the other Alzheimer's risk factors were included in the score, accuracy was 84 percent.
The study is published in the September issue of the Archives of Neurology.
The study is promising but has limitations, said Dr. Ralph Nixon, director of the NYU Center of Excellence on Brain Aging.
The people in the study already had Alzheimer's, so more research is needed to determine if the test is sensitive and specific enough to be used in people with symptoms such as mild cognitive impairment, a risk factor for Alzheimer's.
Diagnosing Alzheimer's disease is typically done through a clinical examination with a neurologist. Neuroimaging tests are done to rule out other conditions causing the mental declines, such as stroke or brain tumors, Nixon said.
Other methods include a spinal tap or specialized MRIs that can detect amyloid protein, but these are not typically available outside of large metropolitan hospitals or as part of medical studies, O'Bryant noted.
"The real major bottleneck in the field is not so much to detect Alzheimer's, which we can do reasonably well once it has progressed, but to detect the earliest signs of the disease, or to be able to distinguish subtle memory impairment that is related to Alzheimer's from other causes of mild memory impairment," Nixon said.
Currently, several medications can help treat the symptoms of memory loss, but none do anything about the underlying causes of the disease, Nixon said.
"The purpose of the biomarkers is to find a way to identify those changes that happen at the very early stage, so that we can nip it in the bud before things get so advanced in the brain; that's [when] it's very difficult to find a medication to reverse it," Nixon said.
Researchers developed the blood test in conjunction with Rules-Based Medicine in Austin, Texas. It has applied for a patent, O'Bryant said.
In a second study from the same journal, researchers from University of Virginia Health System conducted an 18-month trial to test the safety of pioglitazone (Actos), a diabetes drug, for use in Alzheimer's patients.
Though the drug did not improve Alzheimer's symptoms, there were few side effects, according to the study.
Researchers stressed the trial involved only 25 patients and was designed only to test safety, not efficacy, researchers stressed. The next step will be larger trials to test effectiveness.
"There is a lot of encouraging preclinical data that the pathways and the mechanisms this drug would be targeting are highly relevant to the development of Alzheimer's disease," said Nixon, who was not involved in the research. "There is a quite strong rationale for looking at drugs with this type of action."
The study was funded by the National Institutes of Health/National Institute on Aging.
Posted: September 2010