European Journal of Haematology 94 (162–168)

ORIGINAL ARTICLE

Serum cystatin C and serum and urine NGAL in the kidney function assessment of patients with MGUS Agnieszka Stelmach-Goldys1, Bozena Czarkowska-Paczek2, Aleksandra Wyczalkowska-Tomasik3, Leszek Paczek3 1

Department of Hematology, Holycross Cancer Center, Kielce; 2Department of Biophysics and Human Physiology, Medical University of Warsaw, Warsaw; 3Department of Immunology, Transplantology and Internal Diseases, Medical University of Warsaw, Warsaw, Poland

Abstract Objectives: 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. Methodology: 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 k 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. Key words monoclonal gammopathy of undetermined significance; kidney; estimated glomerular filtration rate; cystatin C; neutrophil gelatinase-associated lipocalin Correspondence Bozena Czarkowska-Paczek, MD, Department of Biophysics and Human Physiology, Medical University of Warsaw, Chalubinskiego Str. 5, 02-004 Warsaw, Poland. Tel: +48 22 628 63 34; Fax: +48 22 628 78 46; e-mail: [email protected] Accepted for publication 7 July 2014

Monoclonal gammopathy of undetermined significance (MGUS) was defined in 2010 by the International Myeloma Working Group as follows: serum monoclonal protein (M protein) under 3 g/dL, clonal bone marrow plasma cells under 10%, and an absence of end-organ damage defined as CRAB (hypercalcemia – C, renal insufficiency – R, anemia – A, lytic bone lesions – B) (1). Although MGUS is defined as a condition without any endorgan damage, MGUS patients have excess bone resorption and bone turnover, which results in a higher risk of fracture (2, 3). They also have significantly lower life expectancies

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doi:10.1111/ejh.12413

and higher risks of deep vein thrombosis, bacterial infections, and renal, heart, and liver disorders (4, 5). These conditions occur independently from the malignant transformation. Monoclonal proteins are frequent causes of tubulointerstitial and glomerular kidney injuries (6). Specifically, nephrotoxic free light chains (FLC) cause proximal tubular cell cytotoxicity, activating proinflammatory cytokines and leading to tubulointerstitial nephritis. Ultimately, they could precipitate in distal tubules resulting in further renal damage (7). Pathologies of the glomerular and proximal tubules can

© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd

Stelmach-Goldys et al.

Kidney function in MGUS patients

be associated with low levels of serum M protein and plasma cell clones (

Serum cystatin C and serum and urine NGAL in the kidney function assessment of patients with MGUS.

Monoclonal gammopathy of undetermined significance (MGUS) occurs without other symptoms, although monoclonal proteins can cause kidney injuries. Here,...
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