OBJECTIVETo explore the relationship between serum total light chain κ/λ ratio (sTLC-κ/λ) and proportion of bone marrow plasma cells (BMPC) in patients with IgG type and IgA type multiple myeloma (MM) and its clinical significance.

METHODSThe levels of serum IgG, IgA, κ type and λ type total light chain were detected in 79 newly diagnosed patients with IgG type (n=52) and IgA type (n=27) MM by immuno-nephelometric assay and the sTLC-κ/λ ratio was calculated. The proportion of BMPC was determined by bone marrow smears in the corresponding period, and the changes in sTLC-κ/λ ratio and the proportion of BMPC were observed in 19 patients with IgG type(n=16) and IgA type (n=3) MM undergoing treatment, 26 cases of non-phasmocytic proliferative diseases were enrolled in control group.

RESULTSIn MM patients with IgGκ type and IgAκ type, the sTLC-κ/λ ratio was significantly higher than that in the control group (P<0.01), while in MM patients with IgGλ type and IgAλ type, the sTLC-κ/λ ratio was significantly lower than that in the control group (P<0.01). In MM patients with IgGκ, the sTLC-κ/λ ratio was significantly higher than that in MM patients with IgAκ(P<0.01), while the sTLC-κ/λ ratio in MM patients with IgGλ was significantly lower than that in MM patients with IgAλ. The sTLC-κ/λ ratios in MM patients with IgGκ and IgAκ were positively correlated with the concentrations of IgG (r=0.778,P=0.000) and IgA (r=0.601,P=0.039), while the sTLC-κ/λ ratios of patients with IgGλ and IgAλ were negativily correlated with the IgG(r=-0.586,P=0.01) and IgA level(r=-0.718,P=0.003). In addition, a correlation between each type MM was not found except the IgGκ type MM which had a positive correlation between the sTLC-κ/λ ratio and proportion of BMPC (r=0.579,P=0.002). Nonetheless, 18 of 19 patients with IgG type and IgA type MM undergoing treatment showed concordance between the sTLC-κ/λ ratio and proportion of BMPC change.

CONCLUSIONThere is a lower correlation between the sTLC-κ/λ ratio and the proportion of BMPC in MM patients with IgG type and IgA type, but there is a high concordance between the sTLC-κ/λ ratio and the proportion of BMPC change in the same patient and it suggests that the sTLC-κ/λ ratio plays an important role in the diagnosis and monitoring of IgG type and IgA type MM.