SACRAMENTO, Calif. -- San Francisco researchers have devised a laboratory test to distinguish chronic fatigue syndrome from garden-variety fatigue.
Their discovery, announced yesterday at a national conference on fatigue, might provide the laboratory evidence physicians need to diagnose the debilitating disease, which is thought to afflict 3 to 5 million Americans.
Because it's characterized by often misleading symptoms that mimic everything from mononucleosis to multiple sclerosis, the disease has been difficult to pinpoint. It has been referred to as yuppy flu, chronic Epstein-Barr virus, chronic mononucleosis, chronic devastation syndrome, and myalgic encephalomyelitis.
San Francisco virologist Jay Levy, who along with expert Carol Jessop announced the new test, suggested yesterday another name: chronic immune activation syndrome.
Mr. Levy's name for the disease describes what he and Ms. Jessop found after comparing the immune systems of 120 patients with what they believed to be chronic fatigue syndrome and 80 without. Those with chronic fatigue, researchers reported yesterday, have immune systems that are chronically turned on.
When a healthy immune system reacts to a viral infection, it activates a special set of immune cells consisting of both killer and suppressor types. The killer cells typically reach high enough levels to kill an invading virus or bacteria and are followed by suppressor cells, which return the immune system to normal.
But the white blood cells of patients with chronic fatigue had consistently high levels of killer cells and low levels of suppressor cells.
Mr. Levy and fellow researchers believe the symptoms of chronic fatigue syndrome may be the result of high levels of chemicals called cytokines, used by immune cells to communicate with each other. The symptoms range from swollen lymph nodes to persistent fever, joint and muscle pain, headaches, depression and memory loss.