Early warning values of the kappa/lambda ratio based on serum detection for M-proteinemia diagnosis

Abstract

Objective To introduce the kappa/lambda ratio (K/L) to humoral immunity testing reports to improve the detection rate of M-proteinemia disease. Method Patient samples were accumulated from January 2021 to December 2023 in the First Affiliated People’s Hospital of Soochow University. The positive control group included 156 patients of M-proteinemia. These samples were classified according to light chain positivity. The negative group included samples from 4,722 patients with non-plasma-cell monoclonal disease and 742 healthy individuals. Receiver operating characteristic (ROC) curves were used to check the reliability of K/L for M-proteinemia diagnosis. Results For K-type M-proteinemia, the area under the curve (AUC) was 0.932 when K/L was > 2.39, with a sensitivity of 87.3% and specificity of 92.3%. False positives were mainly found in samples with sicca syndrome (16.67%), mantle cell lymphoma (20.37%), and hepatitis (16.0%). For L-type M-proteinemia, when K/L < 1.44, the AUC was 0.863, the sensitivity was 72.9%, and the specificity was 88.8%. The false positives were mainly found in samples with ANCA-associated systemic vasculitis (21.88%), angioimmunoblastic lymphadenopathy–like T-cell lymphoma (31.25%), NK-/T-cell lymphoma (17.39%), T-cell lymphoma (11.11%), systemic lupus erythematosus (16.83%), cirrhosis (15.69%), infection (12.69%), systemic sclerosis (20.93%), and dermatomyositis (13.95%). False negatives were mainly found in AL (52.0%) and ML (36.36%) . Conclusion K/L > 2.39 and K/L < 1.44 should be used as warning values for M-proteinemia. The content of the heavy chain in IgA- or IgM-type M-proteinemia must be considered to improve the detection rate.