Plasma and Urine Elastase Alpha-1-Proteinase Inhibitor Levels in Neonatal Urinary Tract Infection

Objective: To examine whether plasma or urine elastase α1-proteinase inhibitor (E-α1-PI) levels could be used as a diagnostic marker of urinary tract infection (UTI) in neonates. Subjects and Methods: Plasma and urine E-α1-PI levels were measured by immunoassay in 23 neonates with UTI at the time of admission and 72 h after the onset of treatment and in 10 ‘normal’ neonates (i.e. with trivial problems). Additionally E-α1-PI plasma levels were measured in 15 neonates with septicemia. Results: E-α1-PI plasma levels did not differ between normal neonates and those with UTI. Urine E-α1-PI levels were significantly higher in neonates with UTI on admission compared to normal neonates. A significant decrease in urine E-α1-PI levels was noticed 72 h after the onset of treatment in all but 2 neonates in whom infection persisted. In this study, we have found that the urine E-α1-PI concentration at a cutoff level of 48 µg/l had a sensitivity of 83%, a specificity of 90%, a positive predictive value of 95% and a negative predictive value of 69% for the diagnosis of neonatal UTI. Conclusion: Elevated levels of E-α1-PI in urine seem to be a useful tool for the diagnosis of UTI in neonates (even in those that have already been started on antibiotics) and possibly a valuable marker for early recognition of treatment failure.