Sterile leukocyturia affects urine neutrophil gelatinase-associated lipocalin concentration in type 2 diabetic patients

Introduction: Increased urine neutrophil gelatinase-associated lipocalin (uNGAL) concentrations are associated with the early phase of kidney damage. Urine NGAL may increase due to production by neutrophils present in urine, particularly in patients with urinary tract infections. The aim of the study was to assess the relationship between sterile leukocyturia and uNGAL concentrations in patients with type 2 diabetes (DMt2) at early stages of diabetic kidney disease. Material and methods: The study included 115 DMt2 patients aged 60.0 ±15.5 years, with albuminuria < 300 mg/g creatinine and estimated glomerular filtration rate ≥ 60 ml/min/1.73 m² prospectively recruited at the nephrology ambulatory clinic in 2014-2015. The exclusion criteria were urinary tract infections (excluded by urine culture) and other diseases influencing uNGAL, including inflammatory and other kidney diseases. Urine concentrations of NGAL, albumin and creatinine were measured in the first morning samples, and the urine albumin to creatinine ratio (UACR) and uNGAL to creatinine ratio (UNCR) were calculated. Leukocyturia was detected microscopically. Results: Sterile leukocyturia was present in 15% (95% confidence interval: 9-23%) of patients. Patients with leukocyturia had higher uNGAL and UNCR than patients without leukocyturia. ln(UNCR) correlated with ln(UACR) in the whole group (R = 0.59; p < 0.001) and in patients without leukocyturia (R = 0.56; p < 0.001). In multiple regression, age, ln(UACR), ln(HbA1c) and leukocyturia were independent positive predictors of ln(UNCR). Among patients with leukocyturia, the associations of UNCR with UACR, age and HbA1c were non-significant. Conclusions: In patients with DMt2, the presence of sterile leukocyturia coexists with increased uNGAL and UNCR. Leukocyturia interferes with the relationship between UNCR and UACR or HbA1c.