Persistent Elevation in Urinary Neutrophil Gelatinase-Associated Lipocalin Levels Can Be a Predictor of Urinary Tract Infection Recurrence or Persistence in Women

Women commonly experience urinary tract infection (UTI) recurrence. However, there is no effective tool for predicting recurrent UTI after the first UTI episode. Hence, this study aimed to investigate potential urinary inflammatory biomarkers and specific biomarkers for predicting UTI recurrence or persistence after antibiotic treatment in women. Forty women who had a history of recurrent UTI within 1 year after the initial episode and acute bacterial cystitis were treated with broad-spectrum antibiotics for 1 week. To measure inflammatory biomarker levels, urine samples were collected at the baseline and after 1 week, 1 month, and 3 months. The levels of urinary pro-inflammatory proteins such as neutrophil gelatinase-associated lipocalin (NGAL), nerve growth factor, CXC-motif chemokine ligand (CXCL)-1, interleukin-8, CXCL-10, monocyte chemoattractant protein-1, and tumor necrosis factor-alpha were measured using commercial kits. Seven healthy age-matched women were included as controls. The changes in urinary biomarker levels at the baseline and various time points were compared between women with and without UTI recurrence within 1 month or within 3 months after the initial antibiotic therapy. At the baseline, patients with a higher urinary white blood cell count had a significantly higher NGAL level than the controls and those with a low white blood cell count. Of the 40 patients with a history of recurrent UTI, 12 presented with UTI persistence or recurrence within 1 month and 19 within 3 months after the initial antibiotic treatment. Among the 28 patients without UTI recurrence at 1 month after treatment, 7 had UTI recurrence within 3 months. Compared with patients without UTI recurrence, those with UTI recurrence had significantly higher urinary NGAL levels at 1 week, 1 month, and 3 months after the initial treatment. This study concludes that persistent elevation in urinary NGAL levels after the initial antibiotic treatment indicated persistent bladder inflammation. Further, it could be a predictor of UTI persistence or recurrence within 1 or 3 months after the initial antibiotic treatment. Patients with a history of recurrent UTI and high urinary NGAL levels after antibiotic treatment might require a longer treatment duration to completely eradicate or prevent UTI recurrence.