Defining recurrent urinary tract infection and reinfection risk: electronic health record study

Background There is limited evidence to support the current standard recurrent urinary tract infection (rUTI) definition of ≥2 UTIs within 6 months or ≥3 within 12 months. Information about reinfection risk after meeting criteria for rUTI may aid decisions on the value of prophylactic approaches.

Aim To estimate the risk of subsequent UTI associated with different rUTI definitions.

Design & setting Electronic health record study using Infections in Oxfordshire Research Database (IORD, 2008-2019) and the Clinical Practice Research Datalink (CPRD, 2009-2019).

Method We identified community-acquired UTIs, separated by 28 days, in non-pregnant women aged 16+years. We created candidate rUTI definitions varying the time window from 3-9 months, and the number of UTIs required to meet the definition from 2-3 episodes. For each definition, we calculated Kaplan-Meier risk estimates of subsequent UTIs within 6 and 12 months after meeting rUTI criteria.

Results Of eligible women with at least one UTI, 18% (15,617/84,809) in IORD and 20% (334,487/1,703,088) in CPRD experienced ≥1 rUTI (current definition). The risk of at least two subsequent UTIs within 12 months after meeting the current rUTI definition rose from 17% (IORD) and 16% (CPRD) to 33% (IORD) and 32% (CPRD) under a rUTI definition of ≥3 UTIs within 6 months. Risk of subsequent UTI also increased with age.

Conclusion Risk estimates of subsequent UTIs after a rUTI vary according to the definition of rUTI adopted. Estimates provided here could support shared decision making around UTI prophylaxis and stratification of populations included in future rUTI research.