Diagnostic performance of routine electrophoresis and immunofixation for the detection of immunoglobulin paraproteins (M‐Proteins) in dogs with multiple myeloma and related disorders: Part 1 – Current performance

Abstract

Background: Routine electrophoresis [agarose gel electrophoresis (AGE) and capillary zone electrophoresis (CZE)] and species-specific immunofixation (IF) can be used alone or in combination to detect immunoglobulin paraprotein (M-protein) and diagnose secretory myeloma-related disorders (sMRD). Objective: We aimed to evaluate the performance of AGE, CZE, CZE plus IF (CZE-IF), and AGE plus IF (AGE-IF) for detecting canine serum M-proteins. Methods: One hundred canine cases that had AGE, CZE, and routine IF performed on serum, and where B-cell lineage neoplasia (such as B-cell lymphoma and plasma cell tumors) had been diagnosed or excluded, were evaluated. Routine IF protocols targeted IgG-FC, IgA, and IgM heavy chains and light chains. IgG4 IF and free light chain IF were also performed. B-cell lineage neoplasms with an M-protein detected, using any available method, were classified as sMRD. Datasets from AGE, CZE, IF, CZE-IF, and AGE-IF (electrophoretograms, gel images, and fraction concentrations)were composed and reviewed. The sensitivity, specificity, and Youden's index for Mprotein detection were determined for each dataset. Results:The combination of AGE-IF or CZE-IF was more sensitive (82.9%) than CZE alone (72.0%) or AGE alone (64.6%) and more specific (66.1%, 48.3%, 51.7%, respectively). Immunofixation could be used alone to detect M-proteins (sensitivity 82.9%, specificity 61.9%), but there were technical challenges that complicated the performance and evaluation of the test. Myeloma with free light chains only was found in 5/41 cases of sMRD.Conclusions: Adding routine IF to routine electrophoresis increases the ability to accurately identify M-proteins; however, there is still room for further diagnostic performance improvements.

Detection and Characterization of Paraproteinemia in Canine Chronic B‐cell Lymphocytic Leukemia Using Routine and Free Light Chain Immunofixation

“…Hyperproteinemia and hyperglobulinemia are commonly used as an indication to screen for a monoclonal or biclonal gammopathy. This study agrees with previous work that the lack of hyperproteinemia should not be used as a contraindication for the evaluation of an M‐protein 14 …”

“…The M‐proteins may not have affected the total protein concentration significantly because they were typically present in a low concentration and can be associated with a decrease in other globulins. 14 The median M‐protein concentration was lower than the concentration that was found in many canine multiple myeloma cases. 15 Hyperproteinemia and hyperglobulinemia are commonly used as an indication to screen for a monoclonal or biclonal gammopathy.…”

“…Most patients with a monoclonal protein were not hyperproteinemic. The M‐proteins may not have affected the total protein concentration significantly because they were typically present in a low concentration and can be associated with a decrease in other globulins 14 . The median M‐protein concentration was lower than the concentration that was found in many canine multiple myeloma cases 15 .…”

“…This study agrees with previous work that the lack of hyperproteinemia should not be used as a contraindication for the evaluation of an M‐protein. 14 …”

“…This study agrees with previous work that the lack of hyperproteinemia should not be used as a contraindication for the evaluation of an M-protein. 14 Four cases had M-proteins that were detectable with the anti-fκ IF reagent. This has not been found previously in dogs, but this suggests that this reagent may be diagnostically useful in identifying fLCs in dogs.…”