Abstract
With the introduction of newer platforms for sFLC estimation, more comparative attempts are required to establish an assay-specific reference range, that can be used in the day-to-day clinical management of the patients, as the revised criteria for the diagnosis of myeloma recommend the use of involved Free light chain (FLC)/uninvolved FLC ratio as myeloma defining event, solely relying on Freelite assay. This was an observational study that included 101 patients, 55 (54.5%) with M-protein (myeloma), and 46 (45.5%) without M-protein. The estimation of the sFLC assay was carried out at two separate platforms, the Freelite Assay (The binding Site, Birmingham, UK) on a Siemens BNII Nephelometer, and the N Latex FLC reagent on Atellica NEPH 630 (Siemens Healthineers, Eschborn, Germany). The comparative correlational analysis of the two assays for estimation of κ-, λ FLC, and κ/λ ratio showed a strong to a very strong association (P-value < 0.005) among total patients, however, this was reduced to weak to moderate association among patients with M-protein (P-value < 0.005). The contingency analyses to evaluate the agreement between the assays also showed a similar trend. A better concordance for the κ/λ ratio between the two assays was achieved while expanding this ratio. Our study concluded that two assays showed a better agreement among the patients without M-protein, but these two cannot be used interchangeably for the clinical management of myeloma patients.