(HealthDay News) – Middle-aged and elderly individuals with elevated levels of immunoglobulin free light chains (FLCs), without plasma cell disorders, have a two-fold higher risk of death.

Angela Dispenzieri, MD, from the Mayo Clinic in Rochester, MN, and colleagues measured the levels of Σ FLC (sum of κ and λ FLC) in 15,859 individuals, aged >50 years, without plasma cell disorders. Baseline data were collected from March 1995–November 2003, and participants were followed up through June 2009. The association between Σ FLC and overall survival was assessed.

During 158,003 person-years of follow-up, the researchers recorded 4,348 deaths. Worse overall survival was significantly predicted by a high Σ FLC. Those in the highest 10% of Σ FLC (≥4.72mg/dL) were at much higher risk of death compared with the remaining subjects (risk ratio, 4.4). After adjustment for age, sex, and renal insufficiency, the risk ratio was 2.1. The excess deaths were not restricted to any particular cause.

“We do not recommend this test as a screening test, because it will only cause alarm,” coauthor Vincent Rajkumar, MD, also of the Mayo Clinic, said in a statement. “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.”

The FLC reagent used in the study was provided by Binding Site; several authors disclosed financial ties to Binding Site.

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