{Reference Type}: Journal Article
{Title}: Defining new reference intervals for serum free light chains in individuals with chronic kidney disease: Results of the iStopMM study.
{Author}: Long TE;Indridason OS;Palsson R;Rognvaldsson S;Love TJ;Thorsteinsdottir S;Sverrisdottir IS;Vidarsson B;Onundarson PT;Agnarsson BA;Sigurdardottir M;Thorsteinsdottir I;Olafsson I;Thordardottir AR;Eythorsson E;Jonsson A;Gislason G;Olafsson A;Steingrimsdottir H;Hultcrantz M;Durie BGM;Harding S;Landgren O;Kristinsson SY;
{Journal}: Blood Cancer J
{Volume}: 12
{Issue}: 9
{Year}: Sep 2022 14
{Factor}: 9.812
{DOI}: 10.1038/s41408-022-00732-3
{Abstract}: Serum free light chain (FLC) concentration is greatly affected by kidney function. Using a large prospective population-based cohort, we aimed to establish a reference interval for FLCs in persons with chronic kidney disease (CKD). A total of 75422 participants of the iStopMM study were screened with serum FLC, serum protein electrophoresis and immunofixation. Estimated glomerular filtration rate (eGFR) was calculated from serum creatinine. Central 99% reference intervals were determined, and 95% confidence intervals calculated. Included were 6461 (12%) participants with measured FLCs, eGFR < 60 mL/min/1.73 m2, not receiving renal replacement therapy, and without evidence of monoclonality. Using current reference intervals, 60% and 21% had kappa and lambda FLC values outside the normal range. The FLC ratio was outside standard reference interval (0.26-1.65) in 9% of participants and outside current kidney reference interval (0.37-3.10) in 0.7%. New reference intervals for FLC and FLC ratio were established. New reference intervals for the FLC ratio were 0.46-2.62, 0.48-3.38, and 0.54-3.30 for eGFR 45-59, 30-44, and < 30 mL/min/1.73 m2 groups, respectively. The crude prevalence of LC-MGUS in CKD patients was 0.5%. We conclude that current reference intervals for FLC and FLC ratio are inaccurate in CKD patients and propose new eGFR based reference intervals to be implemented.