Background: Because free light chain assays measure polyclonal as well as monoclonal free light chain components, some previous studies focused on the potential utility of the free light chain assay for detecting chronic immune stimulation, which occurs in autoimmune diseases and allergies. However, most of these trials have been limited to adult patients. In this study, we evaluated the paired serum and urinary free light chain levels of pediatric patients with various inflammatory conditions to investigate the clinical significance of free light chain measurement in pediatrics.
Methods: The study included 227 paired serum and urine specimens from 134 pediatric patients at our hospital between January and February of 2012. Serum and urinary FLC levels were measured using a Freelight Kit (The Binding Site, Ltd., Birmingham, UK).
Results: The serum lambda and urine kappa and lambda components were significantly increased only in the renal impairment group, not in the mild inflammatory group. FLC ratios were not significantly different among these groups.
Conclusions: In serum, only the L components were significantly increased. This result may indicate the presence of a dimeric L structure, in contrast with monomeric K. FLC levels might also be influenced by renal conditions other than mild inflammation. Therefore, as shown in previous studies of adult patients, renal reference ranges might be needed to interpret FLC results, especially for dimeric L components.