Is neutrophil gelatinase-associated lipocalin an optimal marker of renal function and injury in liver transplant recipients?
BACKGROUND
Recently, research has focused on the association of neutrophil gelatinase-associated lipocalin (NGAL) with acute and/or active kidney injury. However, it should be remembered that NGAL is involved in iron metabolism and antimicrobial defense mechanisms.


METHODS
One hundred seven consecutive liver transplant recipients were included in this study. Plasma and urine NGAL levels were measured with the use of enzyme-linked immunosorbent assay. NGAL levels were studied as plasma concentrations (pNGAL), urine concentrations (uNGAL), urinary NGAL to creatinine ratio (uNGAL/Cr), and fractional NGAL secretion (fNGAL).


RESULTS
pNGAL was found to be inversely correlated with estimated glomerular filtration rate (eGFR) and plasma cystatine C (pCysC) (r = -0.26 and P = .007, r = -0.38 and P = .00006, respectively). uNGAL was positively correlated with urinary cystatine C to creatinine ratio (uCysC/Cr) and fractional cystatine C excretion (fCysC) (r = 0.43 and P = .000004; r = 0.4 and P = .1; respectively). uNGAL/Cr was inversely correlated with hematocrit (Htc) and hemoglobin (Hb) (r = -0.35 and P = .0002; r = -0.39 and P = .00004; respectively), and positively correlated with uCysC/Cr (r = 0.5 and P < .0000001). fNGAL was directly correlated with uCysC/Cr and fCysC (r = 0.53 and P < .0000001; r = 0.39 and P = .00005; respectively) and inversely correlated with red blood cell count (RBC; r = -0.31 and P = .001). We observed significant differences of pNGAL, uNGAL/Cr, and fNGAL between sexes, with highest values of uNGAL, uNGAL/Cr, and fNGAL in women and pNGAL in men. In multivariate regression analysis, pNGAL was positively correlated with time elapsed from liver transplantation, neutrophil count, pCysC, and sex (β = 0.36 and P = .00001; β = 0.32 and P = .0001; β = 0.58 and P < .0000001; β = 0.17 and P = .025; respectively) and inversely correlated with patient's age (β = -0.18 and P = .02) with R = 0.67 and R(2) = 0.45, independently from blood glucose, eGFR, RBC, white blood cell count, Hb, uCysC, uCysC/Cr, and fCysC.


CONCLUSIONS
Plasma and urine NGAL levels are strongly correlated not only with kidney function parameters, but also with red and white blood cell parameters and patient's age and sex.
Department of Immunology, Transplantology, and Internal Diseases, Medical University of Warsaw, Warsaw, Poland. Electronic address: elhryniewiecka@gmail.com.
E
E
Hryniewiecka
Department of Immunology, Transplantology, and Internal Diseases, Medical University of Warsaw, Warsaw, Poland.
K
K
Gala
Department of General, Transplant, and Liver Surgery, Medical University of Warsaw, Warsaw, Poland.
M
M
Krawczyk
Department of Immunology, Transplantology, and Internal Diseases, Medical University of Warsaw, Warsaw, Poland.
L
L
Pączek
D058186:Acute Kidney Injury / Q000097:blood* / Q000652:urine*; D000209:Acute-Phase Proteins / Q000652:urine*; D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D015415:Biomarkers / Q000097:blood / Q000652:urine; D003404:Creatinine / Q000097:blood / Q000652:urine; D015891:Cystatins / Q000652:urine; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D000071068:Lipocalin-2; D054834:Lipocalins / Q000097:blood* / Q000652:urine*; D016031:Liver Transplantation; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D011518:Proto-Oncogene Proteins / Q000097:blood* / Q000652:urine*; D012737:Sex Factors; D013997:Time Factors; D055815:Young Adult
D000209:Acute-Phase Proteins; D015415:Biomarkers; D015891:Cystatins; C489506:LCN2 protein, human; D000071068:Lipocalin-2; D054834:Lipocalins; D011518:Proto-Oncogene Proteins; D003404:Creatinine