Urine neutrophil gelatinase-associated lipocalin as a biomarker of adult pyelonephritis

Background: Pyelonephritis is a common infection at any age. Urine neutrophil gelatinase-associated lipocalin (NGAL), a novel biomarker of acute renal failure, is related to pyelonephritis in pediatric patients, although the significance of this urine biomarker in adult patients are not clear. We investigated the relationship between urine NGAL of pyelonephritis and non-pyelonephritis. Patients and methods: We prospectively enrolled adult patients who were hospitalized due to pyelonephritis or non-pyelonephritis. Pyelonephritis was diagnosed in patients with fever and bacteriuria, with no any other infection focuses. Non-pyelonephritis was diagnosed in patients who had fever and another infection focus without bacteriuria. Urine samples were collected on days 0, 3 and 7. Urine NGAL levels were measured by ELISA. Results: There were 35 patients in the pyelonephritis group and 19 patients in the non-pyelonephritis group. Urine NGAL level were significantly higher in the pyelonephritis group than the non-pyelonephritis group on day 0 (median 302 ng/mL vs 25 ng/mL, p = 0.006). The area under the receiver operating characteristic curve of NGAL was 0.78 (p = 0.006). Urine NGAL level had a specificity of 66.7% and sensitivity of 87.0% at the cut-off level of 250 ng/mL for diagnosing pyelonephritis. Conclusions: Urine NGAL level at the diagnosis of infection are elevated in adult patients with pyelonephritis, but not in those with non-pyelonephritis. Urine NGAL might be a supportive biomarker for the diagnosis of pyelonephritis.