Application of capillary electrophoresis in the diagnosis and differential diagnosis of benign and malignant monoclonal gammopathies / 中华检验医学杂志

ABSTRACT

Objective:To evaluate the value of capillary electrophoresis in the diagnosis and differential diagnosis of benign and malignant monoclonal gammopathies (MGs).Methods:A retrospective analysis of the capillary electrophoresis test results of 2 445 newly diagnosed patients at the Affiliated Hospital of Qingdao University from January 2016 to June 2020 was carried out. Capillary zone electrophoresis and immunosubtractive assay were used to detect serum monoclonal protein (MP). The clinical diagnosis and other information of the patients were collected from the clinical database of the Affiliated Hospital of Qingdao University. Kruskal-Wallis rank sum test was used to compare the different amount of monoclonal protein among multiple groups. Receiver operator characteristic curve (ROC) was used to analyze the diagnostic sensitivity and specificity of the monoclonal protein of each type. Youden index was used to calculate the cut-off values.Results:Among the 2 445 patients, 1 183 were positive for monoclonal protein, of which 944 cases were diagnosed as malignant MG, 174 were monoclonal gammopathy of undetermined significance (MGUS), and 65 cases were monoclonal gammopathy of renal significance (MGRS). The percentages of M protein types from high to low is immunoglobulin G(IgG)-κ, IgG-λ, IgA-λ, IgA-κ, free λ light chain, free κ light chain, IgM-κ, double clone, and IgM-λ. The levels of MP of IgG, IgA, IgM and FLC in the malignant MG group were all higher than those in the MGUS group, with statistical significance( P<0.01). The MP levels of IgG and IgA types in malignant MG group were higher than that in MGRS group ( P<0.01). ROC curve analysis showed that the MP of IgG, IgA, IgM and FLC types had good diagnostic efficacy for malignant MG ( P<0.01), and their AUC values were 0.947 (95 %CI 0.926-0.968), 0.930 (95 %CI 0.895-0.966), 0.844 (95 %CI 0.722-0.967) and 0.865 (95 %CI 0.781-0.950), respectively. For IgG, the cut-off value was 14.24 g/L, and the diagnostic sensitivity and specificity were 88.5% and 90.1%, respectively. The cut-off value of IgA was 8.88 g/L, and the sensitivity and specificity of IgA were 87.9% and 81.4%, respectively. For IgM, the cut-off value was 26.93 g/L, and the sensitivity was 64.4% and the specificity was 90.9%. For FLC, the cut-off value, diagnostic sensitivity, and specificity was 7.08 g/L, 85.9%, and 77.8%, respectively. Conclusions:Capillary electrophoresis immunotyping technique can be used to diagnose malignant MG such as multiple myeloma (MM) and non-Hodgkin′s lymphoma (NHL), as well as to screen and track diseases like MGUS and MGRS. Serum MP level can be used to distinguish malignant MG from benign MG effectively.