Efficient use of basic biochemical methods to prove the presence of monoclonal protein in the clinical diagnosis of malignant monoclonal gammopathy

Abstract

Background: This retrospective study evaluates the diagnostic sensitivity of biochemistry methods for the clinical diagnosis of malignant monoclonal gammopathy. In patients with renal insufficiency, renal reference interval as well as standard reference interval is used for evaluating the ratio of free light chains. Methods: We examined samples in 281 patients who were diagnosed with malignant monoclonal gammopathy. The samples were taken at baseline, prior to treatment. Serum and urine protein electrophoresis, serum and urine immunofixation electrophoresis (SIFE+UIFE) and levels of free light chains in serum (FLC) were investigated. Results: Combination of methods with the highest diagnostic sensitivity is the use of maximal number of tests (SIFE+ UIFE + FLC), which identified 98.6% of patients. The achieved results do not statistically significantly differ from the procedure recommended by the International Myeloma Working Group (IMWG) which omitts the urine testing (SIFE + FLC) and identifies 97.9 % of patients (p = 0.523). By using the renal reference ratio of free light chains in patients with renal insufficiency the number of patients identified decreased to the border of significance (p = 0.06) but the number of patients identified by the combination with serum immunofixation (SIFE + FLC) remained the same. Conclusions: The testing algorithm recommended by IMWG for screening patients with the diagnosis of monoclonal gammopathy is effective, diagnostic sensitivity is not significantly lower than the maximal available. Using the renal reference ratio of FLC for evaluation in combination with immunofixation in the serum does not reduce the diagnostic sensitivity of the test and has been reported to increase specificity.