The difference of free light chains as a predictor of kidney damage in patients with Multiple Myeloma

Background: Multiple myeloma (MM) is a malignant neoplasm characterized by the clonal expansion of plasma cells that can release monoclonal immunoglobulins (monoclonal component) or part of theme. Since 2001, the k and λserum free light chains (sFLC) evaluation and their ratio (rFLC) have made up the laboratory analysis more sensitive and precise in MM patients. The role of rFLC has been widely studied and discussed and now it is validated in the literature. Instead, the value of free light chains difference (dFLC), especially in MM is less known yet. The aim of this study is to evaluate the relationship between the dFLC and the kidney damage parameters in patients with MM, in comparison with the rFLC value.Methods: We conducted a retrospective population-based study on 58 MM patients and we individuated two groups obtained considering the measures of dFLC and rFLC in relation to abnormal and normal values of some renal function markers, such us Bence-Jones proteinuria (BJ), albuminuria, proteinuria and serum creatinine. The Mann-Whitney test was used to test the difference between two independent samples. Results: We observed a significant greater mean score of dFLC in patients with abnormal levels of BJ (2322.91>297.47, p=0.0001), albuminuria (2650.61>671.37, p=0.0016) and proteinuria (2327.19>593.14, p= 0.0025), while there was no significant difference for serum creatinine (1636.18<1870.85, p=0.994). Instead, no differences were observed for the rFLC parameter.Conclusion:The data obtained allow us to conclude that dFLC can be considered a potential predictor of renal damage in MM patients, even better than rFLC.