Is Neutrophil Gelatinase–Associated Lipocalin an Optimal Marker of Renal Function and Injury in Liver Transplant Recipients?

BackgroundRecently, 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.MethodsOne 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).ResultspNGAL 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 R2 = 0.45, independently from blood glucose, eGFR, RBC, white blood cell count, Hb, uCysC, uCysC/Cr, and fCysC.ConclusionsPlasma 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.