Table 3.

Study objectives and variables in the ImpresU clinical trial

Objectives		Outcome measures/variables/endpoints	Time point(s) of evaluation of this outcome measure (if applicable)
Primary objective
1	To investigate if methenamine hippurate reduces the need for antibiotic use due to recurrent UTIs (measured as number of antibiotic courses).	Number of UTI antibiotic treatments during the 6 months of treatment. If the participant receives >1 antibiotic course for UTI without symptom relief, it is regarded as one episode and counted as one antibiotic treatment. If there has been an asymptomatic period of at least 14 days in between two UTI antibiotic courses, this is regarded as a new antibiotic treatment.	After 6 months of treatment
Secondary objectives
2a	To investigate if methenamine hippurate will have a prolonged effect on antibiotic usage even after discontinuation.	Number of UTI antibiotic treatments during the 6 months following completion of treatment. If the participant receives >1 antibiotic course for UTI without symptom relief, it is regarded as one episode and counted as one antibiotic treatment. If there has been an asymptomatic period of at least 14 days in between two UTI antibiotic courses, this is regarded as a new antibiotic treatment.	Six months after completing (12 months after commencing) treatment
2b	To investigate if methenamine hippurate reduces the incidence of UTIs.	Number of UTIs (acute symptoms specific/related to the urinary tract) during the 6 months of treatment. If the participant has had >1 UTI episode without symptom relief, it is regarded as one episode. If there has been an asymptomatic period of at least 14 days in between two UTI episodes, this is regarded as a new episode.	After 6 months of treatment
2c	To investigate if methenamine hippurate can reduce severity of UTI symptoms.	Registration of symptom severity when initiating treatment for UTI.	After 6 months of treatment
2d	To investigate if methenamine hippurate can reduce duration of UTI episodes.	Registration of number of days of symptoms during UTI episodes.	After 6 months of treatment
2e	To investigate if number of complications such as pyelonephritis and hospital admission for UTIs differ between methenamine hippurate and placebo.	Registration of number of pyelonephritis and hospital admission for UTI.	Six and 12 months after commencing treatment
2f	To investigate if strain characteristics/phylogenetic subgroups of Escherichia coli found at inclusion are an effect modifier in all the above outcomes.	See above	See above

UTIs, urinary tract infections.