Correlations among different markers determined by immunochemical methods used for the diagnosis and monitoring of intact immunoglobulin multiple myeloma cases

The purpose of this study was to determine the correlations between the concentration of free light chains (kappa, lambda and ratio kappa/lambda) and two other markers, M- protein and pathological total intact immunoglobulin in four groups of patients with intact immunoglobulin multiple myeloma (IIMM) at the diagnosis and during the treatment. In this study 354 samples coming from 46 patients with IIMM were assayed, out of which: 19, IgGkappa; 13, IgGlambda; 7, IgAkappa; 7, IgAlambda. At the diagnosis, immunofixation was positive in all samples and serum protein electrophoresis quantified M- protein for all patients. Free light chains concentrations were abnormal in 92.25% of patients with concentrations above the reference ranges in all patients with IgGkappa and IgAkappa MM. The intact immunoglobulins were elevated in 83.12% of cases. Pearson correlation coefficient showed correlations among the free light chains serum levels (kappa, lambda and ratio kappa/lambda), M- protein and intact immunoglobulins in two groups with IIMM (IgGlambda, IgAlambda). Spearman correlation coefficient values analysis showed that there is a good correlation between M-protein and FLCs (kappa, lambda and ratio kappa/lambda) in three patient groups (IgGkappa, IgGlambda and IgAlambda), excepting IgAkappa myeloma group where the correlation was insignificant. Regarding the intact immunoglobulin, Spearman coefficient showed significant correlations with FLCs concentrations in two groups (IgGlambda and IgAlambda) and an insignificant correlation in the group with IgGkappa MM. For the group of patients with IgAkappa myeloma, the Spearman coefficient showed that IgA concentrations did not correlate with the concentrations of FLCs. The individual correlation (for each patient) among FLCs, M- protein and intact immunoglobulins in 8 patients with IgGkappa IIMM proved to be more significant as compared with the degree of correlation established for the entire group of patients among these markers. Since the values obtained for the studied markers were not homogeneous, we have taken into account the Spearman coefficient values, which indicated the existence ofa correlation between the M-protein, FLCs and intact immunoglobulin.