Combined analysis using extended renal reference range of serum free light chain ratio and serum protein electrophoresis improves the diagnostic accuracy of multiple myeloma in renal insufficiency

ObjectivesTo determine the diagnostic accuracy of serum free light chain κ/λ ratio (rFLC) using extended renal reference (renal range rFLC) in multiple myeloma (MM) with renal insufficiency.Design and MethodsPatients who visited a nephrologist due to renal insufficiency (n = 471) were enrolled. Serum FLC quantification, protein electrophoresis (PEP), and pathologic diagnosis were performed.ResultsRenal range rFLC showed the highest sensitivity to differentiate MM from non-MM among four tests (conventional rFLC, s-PEP, u-PEP). In intact immoglobulin MM (IIMM), the sensitivity and specificity were lower for both rFLCs than for s-PEP. On the other hand, both rFLC showed higher sensitivity compared than PEPs in light chain MM (LCMM). Combined analysis (renal rFLC + s-PEP) increased the sensitivity for both IIMM and LCMM.ConclusionsRenal rFLC is a valuable screening tool in renal insufficiency patients suspected of having MM, especially for LCMM. Combined analysis (renal rFLC + s-PEP) improves the diagnostic accuracy for detecting MM in the setting of renal impairment.

► Renal rFLC showed highest sensitivity for detecting MM in renal impairment patient.
► rFLC showed lower sensitivity and specificity than PEPs for detecting IIMM.
► rFLC had 100% sensitivity for detecting LCMM, whereas PEPs showed low sensitivity.
► Combined analysis using renal rFLC and s-PEP improves the diagnostic accuracy for detecting MM.