Mayo Clinic IDs immune system glitch tied to fourfold higher likelihood of death

Mayo Clinic researchers have identified an immune system deficiency whose presence shows someone is up to four times likelier to die than a person without it. The glitch involves an antibody molecule called a free light chain; people whose immune systems produce too much of the molecule are far more likely to die of a life-threatening illness such as cancer, diabetes and cardiac and respiratory disease than those whose bodies make normal levels.
Researchers studied blood samples from nearly 16,000 people 50 and older enrolled in a population-based study of plasma cell disorders in Olmsted County, Minn. They found that those who had the highest level of free light chains — the top 10 percent — were about four times more at risk of dying than those with lower levels. Even after accounting for differences in age, gender and kidney function, the risk of death was roughly twice as high.
The study suggests that high levels of free light chains are markers of increased immune system response to infection, inflammation or some other serious disorders, says lead researcher Vincent Rajkumar, M.D., a Mayo Clinic hematologist.
Researchers have known that high levels of free light chains are associated with increased risk of death among patients with plasma disorders, such as lymphomas and other blood cancers, but this is the first study to find that high levels of light chains are associated with increased mortality in the general population. Free light chain levels can be measured by using a serum free light chain assay, a simple blood test. This test is often used to monitor light chain levels in patients with plasma disorders such as myeloma to gauge how well they are responding to treatment.
However, Dr. Rajkumar cautions against administering this test with the intent of gauging one’s risk of death.
‘We do not recommend this test as a screening test, because it will only cause alarm,’ Dr. Rajkumar says. ‘We do not know why this marker is associated with higher rates of death. We do not have a way of turning things around. Therefore, I would urge caution in using this test until we figure out what to do about it and what these results mean.’ Mayo Clinic Minnesota