Towards a Reference Standard Definition of Urinary Tract Infection for Research

Urinary tract infection (UTI) is among the most common human bacterial infections. In the context of increasing antibiotic resistance, there are many research efforts to improve the pathophysiological understanding, diagnosis, and treatment of UTI. Despite the high clinical relevance of UTI, there is high variability in definitions in the literature, making interpretation and comparison of research studies difficult, and even impossible in some cases. A recent Delphi consensus study generated a new reference standard definition for UTI that incorporates symptoms, pyuria, and urine culture results. This definition allows for designation of systemic involvement, and no longer categorizes UTIs as complicated or uncomplicated. The definition aligns with guidance from regulatory bodies for approval of UTI drugs. Implementation of a reference standard definition in the design and reporting of future investigations will allow better research design and interpretability within and outside the urology field. The new reference standard resolves some issues and offers a suitable way to unify methodology, and hence increase the potential strength of research in this area. There are some limitations and challenges for implementation, such as difficulties in establishing sensitivity and specificity values for the various settings in which the definition will be used. The inclusion of "probable" and "possible" UTI categories could be a problem in studies that require dichotomous outcomes. Nonetheless, the reference standard should be recommended until new developments become available, notably a more specific UTI biomarker than pyuria. Approaches to standardized diagnosis of catheter-associated UTIs remain unresolved. PATIENT SUMMARY: A new research definition for urinary tract infection (UTI) has been developed. Use of a single standardized definition in research will help in better design of research studies and comparison of results. Although the new definition will help in reducing the variability in UTI research reports, it has some limitations and there may be challenges to overcome before it is widely used.