Assessment of the analytical performance and the sensitivity of serum free light chains immunoassay in patients with monoclonal gammopathy.

OBJECTIVES: A new immunoassay which quantifies Kappa, Lambda free light chains (FLC) and a ratio of Kappa to Lambda FLC has been reported to be sensitive for detecting a variety of FLC diseases. We assessed the analytical criteria and the diagnostic performance of this immunoassay in patients who present a monoclonal gammopathy. DESIGN AND METHODS: Quantification of FLC, serum protein electrophoresis (SPE) and immunofixation (IFE) were performed on patients who present a monoclonal gammopathy of undetermined significance (MGUS), an intact immunoglobulin multiple myeloma (IIMM) or a light chain multiple myeloma (LCMM). RESULTS: The monoclonal component was identified by IFE in the sera of all patients. Based on the diagnostic reference range, the ratio of Kappa to Lambda FLC was abnormal in 25% of the tested population, compared to 94% for SPE in MGUS patients. For IIMM and LCMM, the FLC ratio was abnormal in 70% and 100% of the population, compared to 85% and 40% for SPE, respectively. CONCLUSION: SPE and IFE have a higher sensitivity for identifying MGUS and IIMM.

Transfusion support of autoimmune hemolytic anemia: how could the blood group genotyping help?

Conventional pretransfusion testing based on hemagglutination assays can be challenging for patients with autoimmune hemolytic anemia (AIHA) because of the presence of auto-antibodies. It has been suggested that deoxyribonucleic acid-based methods could be more efficient in the selection of antigen-matched red blood cell units in those settings. Because of the high risk of alloimmunization of these patients and the labor-intensive nature of adsorption techniques, we decided to evaluate the feasibility of selecting antigen-matched units on the basis of RBC genotyping. We included in our routine RBC genotyping program samples from 7 patients with AIHA presenting a strongly positive direct antiglobulin test. This made the routine compatibility tests difficult. Most patients had previously received transfusions because of warm AIHA. Matched donor units were selected according to the genotype. For all but 1 patient, blood group genotyping could be done on time to allow antigen-matched transfusion. Four patients received antigen-matched red blood cell units based on RBC genotyping and for 1 patient the fact that no matched units were available led us to postpone the transfusion. After each transfusion, the recovery was recorded and considered satisfactory for all transfused patients.