title: The association of serum-free light-chain levels with markers of renal function.
abstract: BACKGROUND
  The kidney is often affected in plasma cell dyscrasias, usually due to the effects of nephrotoxic monoclonal-free light chains. Renal failure due to a monoclonal gammopathy may be detected by the highly sensitive serum-free light-chain (sFLC) ratio yet missed by electrophoretic assays. The aim of this study was to assess sFLC levels in relation to markers of renal function.
  
  
  METHODS
  Five-hundred thirteen patients were included in this study. sFLC levels were measured by Freelite® (The Binding Site Group Ltd, Birmingham, UK) assay using the BNII nephelometer (Siemens Diagnostics, Germany). Kappa/lambda (κ/λ) sFLC ratio was calculated. Serum creatinine levels were analyzed by modified Jaffe method in Cobas 8000 analyser. GFR was estimated by the CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) equation. Patients were assigned to two groups depending on their eGFR values: ≤ 60 mL/min/1.73 m(2) (Group 1, n = 103) and > 60 mL/min/1.73 m(2) (Group 2, n = 410). Data were expressed as median and min-max. All the statistical analyses were done with SPSS version 20.0 and a significance level of 0.05 was considered.
  
  
  RESULTS
  Serum κ-FLC median value was 36.4 (5.62-16,000) mg/L, serum λ-FLC was 21.7 (4.91-8770) mg/L, κ/λ sFLC ratio was 1.33 (0.01-3258) and serum creatinine was 1.56 (0.63-7.21) mg/dL in Group 1. Both λ sFLC and κ/λ sFLC ratios were correlated with eGFR (r = -0.318, r = 0.198, p < 0.05, respectively). We did not find any significant correlation between κ/λ sFLC ratio and eGFR in Group 2.
  
  
  CONCLUSIONS
  We examined the association between sFLC concentrations and renal function. Our preliminary findings suggest that serum λ-FLC might be considered as a useful marker for predicting renal function. Prospective studies are needed to clarify the usefulness of these parameters for identifying renal failure due to a monoclonal gammopathy.
authors.affiliation: a Department of Biochemistry and.
authors.forename: Bilge Karatoy
authors.initials: BK
authors.lastname: Erdem
authors.affiliation: a Department of Biochemistry and.
authors.forename: Fatih
authors.initials: F
authors.lastname: Davran
authors.affiliation: b Division of Nephrology, Department of Internal Medicine, Faculty of Medicine , Akdeniz University , Antalya , Turkey.
authors.forename: Vural Taner
authors.initials: VT
authors.lastname: Yilmaz
authors.affiliation: b Division of Nephrology, Department of Internal Medicine, Faculty of Medicine , Akdeniz University , Antalya , Turkey.
authors.forename: Ramazan
authors.initials: R
authors.lastname: Çetinkaya
authors.affiliation: a Department of Biochemistry and.
authors.forename: Halide
authors.initials: H
authors.lastname: Akbas
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers / Q000097:blood; D015331:Cohort Studies; D018450:Disease Progression; D005260:Female; D006801:Humans; D007147:Immunoglobulin Light Chains / Q000097:blood*; D007145:Immunoglobulin kappa-Chains / Q000097:blood; D007677:Kidney Function Tests; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011379:Prognosis; D051436:Renal Insufficiency, Chronic / Q000097:blood* / Q000503:physiopathology*; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D055815:Young Adult
chemical_list: D015415:Biomarkers; D007147:Immunoglobulin Light Chains; D007145:Immunoglobulin kappa-Chains
keywords: Kappa sFLC; lambda sFLC; renal function; sFLC ratios; serum-free light chains