Modern approaches to the detection of monoclonal gammopathy of undetermined significance (MGUS) in patients with kidney diseases

Monoclonal gammopathy (MG) is not only the state preceding of hematological neoplasms, but also associated with non - hematological diseases, in particular kidney damage. Aim. To assess the diagnostic value of “Freelite” methods in addition to electrophoresis (EF) and immunofixation (IF) of serum and urine proteins for detecting MG in patients with kidney diseases. Materials and methods. 87 patients with kidney damage, in which MG was established using the method of electrophoresis of serum proteins (EF), immunofixation (IF) and the method of free light chains determination - FLC “Freelite” were selected. The diagnostic value of three - component serum panel was compared with EF and IF. Results and discussion. AL-amyloidosis with kidney involvement was diagnosed in 41% patients, cryoglobulinemic glomerulonephritis (cryo GN) - in 18%, chronic glomerulonephritis (CGN) - in 35%, also there was small number of patients with light chain disease and cast - nephropathy. Determination of MG using EP was possible only in 38 (44%). Adding to the serum electrophoretic methods instead of the “Freelite” method, the urine EF and IF reduced the number of missed patients with monoclonal gammopathy from 24 (27%) to 11 (13%), including in the subgroup of patients with AL-amyloidosis but did not reach the sensitivity of the three - component serum screening panel. In 10 (11.5%) MG was represented only by intact mIg with one type of light chain, either κ or λ. Most often - in 25% of patients, intact monoclonal gammopathy was observed in HCV (+) cryo GN. A combination of intact mIgM, mIgG or mIgA with mFLC, was detected in 37 (42.5%). In almost half (46%) of the patients, only mFLC was detected - an abnormal κ/λ ratio. Conclusion: The serum screening panel EF + IF + “Freelite” spreads the low - grade monoclonal gammopathy recognition (MGUS) and should be included in the algorithm of examining patients with kidney disease.