Monoclonal vs polyclonal free light chain assays.

Am J Clin Pathol 2009;131:897-903 901 © American Society for Clinical Pathology relative to Freelite (Figure 1). Both patients had negative results for urine BJPs, further undermining the validity of the ELISA assay results. It is possible that the monoclonal antibodies are cross-reacting with the reported IgG λ and IgA λ monoclonal intact immunoglobulins in these patients, leading to falsely raised λ FLC results. Suggestions by Davern and colleagues1 that Freelite antisera regularly underestimate results due to missing a wide variety of λ subgroups, are affected by instrumentation and “unknown” technical issues, and are confounded by interference from intact immunoglobulins are not supported by their data. The results reported and views expressed in the article should be compared with the scientific consensus in the many, larger, and more rigorous evaluations of Freelite already published.