Upper and lower urinary tract infections can be detected early but not be discriminated by urinary NGAL in adults

We investigated whether the recently established biomarkers of acute kidney injury, neutrophil gelatinase-associated lipocalin (NGAL) and kidney injury molecule-1 (KIM-1), may help to diagnose acute urinary tract infections (UTI) in adults and are able to distinguish between upper or lower localization. NGAL levels were measured in blood and urine, and KIM-1 concentrations in urine of 97 subjects. We recruited age- and gender-matched groups of 30 patients with acute upper UTI and 29 patients with acute lower UTI as well as 38 healthy controls. NGAL and KIM-1 were determined by ELISA, serum and urine creatinine applying the Jaff,'s method. Urinary NGAL (uNGAL) was significantly increased in patients with upper as well as with lower UTI compared with the healthy controls (P < 0.01; P < 0.05). Accordingly, uNGAL normalized on urinary creatinine (uNGAL/uCrea) was markedly higher in patients with lower UTI compared with the control group (P < 0.05), and uNGAL/uCrea levels were still raised in patients with upper UTI, though not reaching statistical significance (P = 0.07). However, neither uNGAL nor uNGAL/uCrea levels displayed significant differences between patients with upper or lower UTI (P = 0.75; P = 0.97). uKIM-1 levels were close to the detection limit and too low to reliably reveal differences between the three groups. While uKIM-1 seems not to serve as a helpful biomarker in this setting, increased levels of uNGAL indicate inflammatory processes in the urinary tract in adults. However, the determination of uNGAL levels does not allow to differentiate between upper and lower UTI.