Difficulties in immunofixation analysis: a concordance study on the IFM 2007-02 trial

Abstract

Multiple myeloma response is evaluated according to the International Myeloma Working Group Uniform Criteria.1 Among these criteria, serum electrophoresis has a pivotal role as it represents the first step to detect the persistence of the monoclonal protein identified at diagnosis, while performing immunofixation tests in case of normalized electrophoresis. Interpretation of immunofixation according to diagnosis profile is sometimes difficult and requires a careful examination, especially when very thin bands are observed. Indeed, atypical serum immunofixation patterns,2 also named oligoclonal bands3 or small abnormal protein bands,4 have been often reported following not only allogeneic transplantation but also autologous transplantation and even following intensive chemotherapy for leukemia. In fact, if no monoclonal component is detected by serum protein electrophoresis, immunofixation interpretation with bone marrow evaluation determines the type of response, stratifying patients between complete response (CR) and a very good partial response (VGPR).1 Because immunofixation interpretation is based on human evaluation, it presents a certain degree of subjectivity that conditions its performances. The purpose of this work was to estimate the inter-operator variability and intra- and inter-laboratory performances.