Wilson 2005.

Methods	Study design: prospective, randomized controlled study Study dates: not reported Setting: Auckland Hospital Country: New Zealand
Participants	Inclusion criteria: undergoing diagnostic flexible cystoscopy Exclusion criteria: undergoing therapeutic intervention; e.g. stent removal or bladder biopsy; requiring intravenous antibiotic prophylaxis or already taking antibiotics Sample size: 263 participants recruited, but 29 excluded because of incomplete data acquisition, leaving 234 for analysis Age: not reported Sex: control group: 91 men and 31 women; treatment group: 85 men and 27 women
Interventions	Group 1 (n = 122): placebo 20–60 minutes before flexible cystoscopy Group 2 (n = 112): norfloxacin 400 mg orally 20–60 minutes before flexible cystoscopy
Outcomes	Symptomatic UTI How measured: participants were questioned by a nurse by telephone regarding symptoms of UTI, UTI was defined as urinary symptoms associated with significant growth (> 102 CFU/mL) on urine culture Time points measured: urine culture performed at days 3 and 7 after flexible cystoscopy Time points reported: not reported Outcomes: 1/122 participants in control group and 1/112 in treatment group had symptomatic UTI. The infection in the placebo group occurred de novo, while the participant in the norfloxacin group had bacteriuria before the procedure Asymptomatic bacteriuria How measured: not reported Time points measured: urine culture performed at days 3 and 7 after flexible cystoscopy Time points reported: not reported Outcomes: 3/122 participants in control group and 1/112 participants in treatment group had asymptomatic bacteriuria
Funding sources	No information about funding
Declarations of interest	No information about conflict and interest
Notes	We tried to contact corresponding author regarding the random sequence generation and allocation method, but received no response.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "The pharmacy department of Auckland Hospital provided both antibiotic and placebo in randomized numbered packs, which were blinded to the patient, clinic nurse, and the physician performing the procedure." Comment: method for generation of random sequence was not given.
Allocation concealment (selection bias)	Unclear risk	Comment: no information regarding concealment of randomization.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Quote: "The pharmacy department of Auckland Hospital provided both antibiotic and placebo in randomized numbered packs, which were blinded to the patient, clinic nurse, and the physician performing the procedure." Comment: blinding of participants and personnel performed adequately.
Blinding of outcome assessment (detection bias) Subjective outcomes	Low risk	Quote: "Principal investigator could not identify participants received the active drug or not, and participants were blinded about their treatments." Comment: double‐blind study. Risk of detection bias for symptomatic UTI and asymptomatic bacteriuria was low.
Blinding of outcome assessment (detection bias) Objective outcomes	Unclear risk	Comment: not applicable, since the objective outcome of drug resistance was not reported.
Incomplete outcome data (attrition bias) Systemic UTI	Unclear risk	Comment: outcome not reported.
Incomplete outcome data (attrition bias) Symptomatic UTI	Unclear risk	Quote: "263 patients were recruited, but 29 were excluded because of incomplete data acquisition, leaving 234 for analysis." Comment: 234/ 263 recruited participants (122 in control group, 112 in intervention group) were included for analysis of this outcome, 29 excluded because of incomplete data acquisition. No information about whether these dropouts were before or after randomization or to which group dropouts belonged. Study was stopped and interim analysis performed because of low recruitment rate.
Incomplete outcome data (attrition bias) Serious adverse events	Unclear risk	Comment: outcome not reported.
Incomplete outcome data (attrition bias) Minor adverse events	Unclear risk	Comment: outcome not reported.
Incomplete outcome data (attrition bias) Localized UTI	Unclear risk	Comment: outcome not reported.
Incomplete outcome data (attrition bias) Asymptomatic bacteriuria	Unclear risk	Quote: "263 patients were recruited, but 29 were excluded because of incomplete data acquisition, leaving 234 for analysis." Comment: 234/263 recruited participants (122 in control group, 112 in intervention group) were included for analysis of this outcome, 29 excluded because of incomplete data acquisition. No information about whether these dropouts were before or after randomization or to which group these dropouts belonged. Study was stopped and interim analysis performed because of low recruitment rate.
Incomplete outcome data (attrition bias) Bacterial resistance	Unclear risk	Comment: outcome not reported.
Selective reporting (reporting bias)	Unclear risk	Comment: data reported on all outcomes specified in methods section, but there was no access to trial protocol/registration to further assess selective reporting.
Other bias	Low risk	Comment: no other bias detected.

CFU: colony‐forming units; n: number of participants; SD: standard deviation; UTI: urinary tract infection.