Early identification of tubulointerstitial renal injury in hypertensive patients: a comparative evaluation of the urine biomarkers NGAL and KIM 1

Objective. The aim of the study was a comparative assessment of urine NGAL (neutrophil gelatinase associated lipocalin) and KIM‑1 (kidney injury molecule‑1) as biomarkers of early detection of tubulointerstitial renal damage in patients with arterial hypertension (HTN) without concomitant diabetes mellitus and kidney disease. Design and methods. The study involved 52 patients of both sexes (17 man and 35 women, mean age 60,2 ± 6,54 years) hospitalized for aggravation of HTN 1–3 degrees, which were divided into 3 groups with glomerular filtration rate (GFR) > 90 ml/min/1,73 m 2 (n = 21), 60–90 ml/min/1,73 m 2 (n = 19) and < 60 ml/min/1,73 m 2 (n = 12). In a separate group, patients with albuminuria in the range 10–29 mg/g urine creatinine were isolated. The comparison group consisted of 15 normotensive individuals (6 men and 9 women, mean age 49,8 ± 9,68 years) with no obvious signs of renal, cardiovascular or other diseases. All patients and controls underwent examination, and albumin, NGAL (Human NGAL ELISA kit) and KIM‑1 (Human KIM‑1 Immunoassay ELISA) levels were assessed in the first morning urine portion. Results. In the group of patients with GFR 67,7 ± 4,92 ml/min/1,73 m 2 (mildly reduced kidney function) and in the group of patients with GFR 55,8 ± 4,44 ml/min/1,73 m 2 (renal dysfunction) urine NGAL level increased by 3,43 (р < 0,05) and 3,92 times (р < 0,05), respectively, as compared with the control group. The urine concentration of KIM‑1 increased by 2,06 times (р < 0,05) was observed only in patients with renal dysfunction. Based on the ROC analysis AUC for the urine NGAL level in patients with mildly reduced kidney function is 0,78 (95 % confidence interval, 95 %CI: 0,70–0,86; p < 0,001), specificity — 89,6 %, sensitivity — 66,7 %. Similar indicators for KIM‑1 are 0,72 (95 % CI: 0,64–0,80; p < 0,001), specificity — 85,3 %, sensitivity — 16,7 %. In the group of patients with mildly reduced kidney function the urine level of NGAL correlated with the HTN severity (r = 0,8944, р < 0,001) and its duration (r = 0,8953, р < 0,001). Conclusions. Urine NGAL as compared with KIM‑1 is a more sensitive biomarker, which indicates tubulointerstitial injury in HTN patients without diabetes mellitus and kidney diseases in the early stage of impairment renal function.