title: Serum cystatin C and serum and urine NGAL in the kidney function assessment of patients with MGUS.
abstract: OBJECTIVE
  Monoclonal gammopathy of undetermined significance (MGUS) occurs without other symptoms, although monoclonal proteins can cause kidney injuries. Here, we assessed kidney function and identified the best follow-up parameters in patients with MGUS without kidney damage symptoms.
  
  
  METHODS
  Forty-six patients with MGUS were included in the study group. The control group (CRT, n = 23) consisted of healthy subjects matched for age and sex. Serum cystatin C was determined using an immunonephelometric method, serum and urine neutrophil gelatinase-associated lipocalin (NGAL) was measured with an immunoenzymatic method, and cathepsin B activity was determined fluorometrically.
  
  
  RESULTS
  Serum cystatin C and urine NGAL were higher, and serum NGAL was lower in MGUS patients compared with CRT. Neither serum cystatin C, nor serum or urine NGAL, correlated with the biomarkers of MGUS. The serum activity of cathepsin B did not differ between groups and did not correlate with serum cystatin C. Serum cystatin C correlated with serum creatinine, while serum NGAL did not correlate with serum creatinine or cystatin C. The estimated glomerular filtration rates (eGFRs) in MGUS were within normal range and correlated with serum cystatin C. The strongest correlation was observed for CKD-EPI. Seven patients presented with albuminuria >30 mg/day. There was a correlation between albuminuria in this group and λ free light chains.
  
  
  CONCLUSIONS
  The kidney function in MGUS patients is impaired, although there are no clinical and standard laboratory test manifestations. Cystatin C and urine, but not serum, NGAL should be considered markers for kidney injury. CKD-EPI is recommended for eGFR assessment.
authors.affiliation: Department of Hematology, Holycross Cancer Center, Kielce, Poland.
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Stelmach-Goldys
authors.forename: Bozena
authors.initials: B
authors.lastname: Czarkowska-Paczek
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Wyczalkowska-Tomasik
authors.forename: Leszek
authors.initials: L
authors.lastname: Paczek
mesh_terms: D000209:Acute-Phase Proteins / Q000652:urine*; D000368:Aged; D015415:Biomarkers / Q000097:blood / Q000652:urine; D016022:Case-Control Studies; D055316:Cystatin C / Q000097:blood*; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007677:Kidney Function Tests; D000071068:Lipocalin-2; D054834:Lipocalins / Q000097:blood* / Q000652:urine*; D008297:Male; D008875:Middle Aged; D008998:Monoclonal Gammopathy of Undetermined Significance / Q000097:blood* / Q000652:urine*; D011518:Proto-Oncogene Proteins / Q000097:blood* / Q000652:urine*
chemical_list: D000209:Acute-Phase Proteins; D015415:Biomarkers; D055316:Cystatin C; C489506:LCN2 protein, human; D000071068:Lipocalin-2; D054834:Lipocalins; D011518:Proto-Oncogene Proteins
keywords: cystatin C; estimated glomerular filtration rate; kidney; monoclonal gammopathy of undetermined significance; neutrophil gelatinase-associated lipocalin