N Latex FLC serum free light-chain assays in patients with renal impairment

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The aim of this study was to establish ranges for N Latex free light-chain (FLC) monoclonal-based nephelometric assays in patients with renal impairment.


In this retrospective study, serum samples from 284 patients with chronic kidney disease (CKD) stages 1-5 were measured with N Latex and Freelite™ FLC reagents on the Siemens BN™II system and compared with controls without renal impairment.


Both κFLC and λFLC concentrations increased with the N Latex FLC and the Freelite™ assays with each increment in CKD stage. No difference was found in FLC κ concentrations between the two methods. In patients with renal failure, N Latex FLC detected higher concentrations of λFLC (CKD5 median, 128 mg/L; 95% range, 43-302) compared with Freelite™ (89.5 mg/L, 35-197) (p<0.0001). This resulted in significantly different κ/λ ratios in patients with CKD for the two tests. The Freelite™ κ/λ ratio in the CKD5 group (median, 1.22; min-max, 0.22-2.70) was significantly increased compared with healthy controls (p<0.0001), and several individual samples were outside the reference range for healthy controls (0.26-1.65). In contrast, none of the 284 patients with CKD had an FLC κ/λ ratio exceeding the N Latex reference limits for healthy controls (0.31-1.56). The N Latex FLC κ/λ ratio in the CKD5 group (0.69, 0.32-1.54) was significantly lower compared with the control group (p<0.0001).


These findings demonstrate that the N Latex FLC κ/λ ratio in patients with renal failure did not differ from the reference limits for healthy controls.

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