The researchers — senior author Ronald W. Davis, a professor of biochemistry and of genetics at the Stanford School of Medicine; lead author Rahim Esfandyarpour, a University of California-Irvine assistant professor of electrical engineering and computer science, and their colleagues — published their breakthrough in a paper online in the "Proceedings of the National Academy of Sciences" in late April.
Prior to their assay, no standard test had been devised to diagnose myalgic encephalomyelitis/chronic fatigue syndrome. The disease, which is little understood and often discounted as a psychological condition, causes a constellation of symptoms. The most pronounced aspect is extreme exhaustion exacerbated by stimuli and mental and physical activity. The sufferer cannot recover through normal rest or sleep. The disease appears to affect multiple organ systems in the body.
An estimated 836,000 to 2.5 million Americans have chronic fatigue syndrome, according to the U.S. Centers for Disease Control, but some researchers estimate that more than 91 percent of patients with the illness have not yet been diagnosed.
Several studies have found the disease might be triggered by a combination of factors such as major life stressors, viral infection, stomach viruses, bacterial infections, toxin exposure, immunodeficiency, nutritional deficiencies, genetic susceptibility and several other contributors, the researchers noted.
Davis, of Palo Alto, has been searching for identification markers for the disease since his son, Whitney Dafoe, came down with a severe case of the disease a decade ago.
The test could also help others from experiencing what his family has encountered over the years.
"It should put a stop to doctors telling patients that there is nothing wrong with them or that it's only in their heads or a 'false illness belief.' I believe this will be a big step for millions of patients. We are working hard to make it usable easily and cheaply for doctors," Davis said in a email.
Tests that would normally guide a doctor's diagnosis — of a patient's liver, kidneys, heart function, blood and immune cell counts — "for chronic fatigue syndrome patients, the results all come back normal," Davis, a genetics researcher who was instrumental in the Human Genome Project, said.
In their study, the researchers chose patients with moderate-to-severe chronic fatigue syndrome. They focused on peripheral blood mononuclear cells, which are blood cells that are critical for the immune system to fight infection and adapt to invasive pathogens.
The assay measured changes in amounts of energy flowing from thousands of sensors in the assay through the plasma and immune cells they extracted from the chronic fatigue and the healthy participants' blood. The scientists stressed the samples using salt, a commonly used stressor in studies on plant, yeast, bacteria, mice and human cells. They compared how the blood components from the healthy and chronic fatigue patients affected the flow of the electrical current. The blood samples from all of the chronic fatigue syndrome patients showed a clear spike in the electric current, a sign the cells and plasma are incapable of effectively processing the salt stressor. Samples from the healthy patients were relatively even.
"We don't know exactly why the cells and plasma are acting this way, or even what they're doing. But there is scientific evidence that this disease is not a fabrication of a patient's mind. We clearly see a difference in the way healthy and chronic-fatigue-syndrome immune cells process stress," Davis said.
The researchers are now expanding their testing with more participants to confirm their findings.
The assay is also being used to test FDA-approved drugs or those that will soon be available to the public to find potential treatments. A drug that seems to reduce the spike in the electrical current could indicate it is facilitating the immune cells and plasma to process stress, researchers said.
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