Diagnostic thresholds for free light chains in multiple myeloma depend on the assay used

Abstract

Leukemia accepted article preview online, 20 November 2017. doi:10.1038/leu.2017.335.

Comparison of 2 Serum-Free Light-Chain Assays in CKD Patients

“…10,15 The k/l ratio is higher for Freelite than N Latex for values >1 (by Freelite), as we reported previously. 15 As FLC measurement is increasingly important in the diagnosis and monitoring of paraprotein-related kidney diseases, we were particularly interested to analyze the effect of kidney dysfunction on the 2 available FLC assays. In both assays, k and l FLC correlate inversely with eGFR, but this effect is more pronounced in l FLC measurement by N Latex.…”

“…As reported previously, k FLCs are in general higher by Freelite than by N Latex. 15 In contrast, l FLCs are higher by N Latex. 10,15 The k/l ratio is higher for Freelite than N Latex for values >1 (by Freelite), as we reported previously.…”

“…15 In contrast, l FLCs are higher by N Latex. 10,15 The k/l ratio is higher for Freelite than N Latex for values >1 (by Freelite), as we reported previously. 15 As FLC measurement is increasingly important in the diagnosis and monitoring of paraprotein-related kidney diseases, we were particularly interested to analyze the effect of kidney dysfunction on the 2 available FLC assays.…”

Comparison of three different serum-free light-chain assays—implications on diagnostic and therapeutic monitoring of multiple myeloma

“…So far, only a limited number of comparison studies between the different assays exist. Previous comparisons between N Latex and Freelite assay [14][15][16][17][18][19] and between Sebia FLC and Freelite assay 13,20,21 have shown discrepancies in determination of light-chain values and κ/λ ratio. In comparison analyses between Freelite and N Latex FLC, and between Freelite and Sebia FLC, absolute FLC concentrations measured by Sebia FLC or N Latex FLC were lower compared with Freelite.…”

“…Two recently published studies showed that the diagnostic thresholds for iFLC/niFLC ratio ≥ 100 proposed for Freelite do not apply to N Latex FLC and Sebia FLC. New thresholds for N Latex FLC (iFLC/niFLC ratio ≥ 30) and for Sebia FLC (iFLC/niFLC ratio ≥ 16) were proposed 14,20 . This is very important clinically because, due to different results of FLC assays, patients may not be detected as MM patients requiring treatment, responses might not be evaluated consistently, and treatment decisions may be "test-dependent" and not truly disease dependent.…”