Distinguishing asymptomatic bacteriuria from urinary tract infection in the elderly – the use of urine levels of heparin-binding protein and interleukin-6

Asymptomatic bacteriuria (ABU) is highly prevalent among elderly patients. It can be difficult to distinguish ABU from symptomatic urinary tract infection (UTI) in this population, which leads to unnecessary antibiotic treatment. Urinary heparin-binding protein (U-HBP) and urinary interleukin-6 (U-IL-6) have previously been studied as diagnostic markers for UTI. In this study, biomarkers were measured in the urine of 134 nursing home residents. The prevalence of ABU in this population, excluding patients with urinary catheter, was 32.8%. Levels of U-HBP and IL-6 were significantly lower among residents with ABU when compared to 49 patients with verified UTI. When previously defined cut-off limits were used, U-HBP had a high negative predictive value for UTI (93%), however, the specificity for differentiating patients with UTI and ABU was low. Discriminatory values were better for U-IL-6 with a sensitivity of 80% and specificity of 82% for the differentiation between the subgroup of pyelonephritis and ABU.