Immunotyping as an Alternative to Reducing Agents for Resolving Monoclonal Immunoglobulin Aggregates Observed on...

Polymerized immunoglobulins can be difficult to interpret when observed on serum immunofixation electrophoresis (IFE). The use of reducing agents, such as beta-mercaptoethanol (BME), has been instrumental in resolving cases in which the monoclonal protein is unidentifiable due to polymerization. However, this procedure can be inconvenient to laboratories. We therefore investigated the use of immunotyping (IT) to resolve immunoglobulin aggregates as a potential replacement for BME pretreatment.

Patient samples with paraprotein polymerization were selected from our routine testing and interpretation workflow in the protein immunology laboratory. Identified specimens were subjected to both repeat IFE testing after BME treatment and IT without BME treatment. Results from both types of repeat testing were compared to each other and to patient history if available. IFE was performed on a Hydrasys 2 (Sebia), and IT was performed on a Capillarys 3 Tera (Sebia).

Five patient samples were identified with an aggregate band visible in all IFE lanes. Results of BME treatment with repeat IFE or IT using the original sample were 100% concordant. One patient was determined to have no monoclonal protein, 3 had immunoglobulin M (IgM) lambda monoclonal proteins, and one had an IgM kappa monoclonal protein.

IT was able to successfully identify paraproteins without the use of BME in samples that were difficult to interpret using IFE due to polymerization. This finding suggests that routine protocols for IT can be used in lieu of a secondary protocol and additional resources for BME treatment prior to IFE analysis.