Goh 1982.

Methods	Study design: randomized controlled trial Study dates: not reported Setting: not reported Country: Singapore
Participants	Inclusion criteria: attending for check cystoscopy for previous bladder neoplasms, or for primary investigation of haematuria Exclusion criteria: not reported Sample size: 420 participants randomized and 31 participants had bacteriuria present at cystoscopy and were excluded. Age (years): mean control group: 66.5 (SD 15.64); mean treatment group: 63.2 (SD 14.43) Sex: not reported
Interventions	Trial A Group 1 (n = 111): no antibiotic prophylaxis Group 2 (n = 93): 2 tablets each containing trimethoprim 80 mg + sulphamethoxazole 400 mg twice daily for 2 days after cystoscopy Trial B Group 3 (n = 95): no antibiotic prophylaxis Group 4 (n = 90): 1 tablet containing trimethoprim 160 mg + sulphamethoxazole 800 mg, taken once after cystoscopy
Outcomes	[Bacteriuria] How measured: urine samples with count of organisms > 105 CFU/mL Time points measured: midstream urine samples 5 days after cystoscopy Time points reported: not reported Outcomes: trial A: control group: 34/111 participants had bacteriuria after cystoscopy; treatment group: 5/93 had bacteriuria after cystoscopy; trial B: control group: 17/95 had bacteriuria after cystoscopy; treatment group: 5/90 had bacteriuria after cystoscopy
Funding sources	No information about funding
Declarations of interest	No information about conflict and interest
Notes	1 participant developed Escherichia coli septicaemia, an incidence of 0.2%, from the trial B control group with no existing bacteriuria. No email address available for contacting the corresponding author for further information.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "In both trials patients were randomly allocated into a control group and a study group." Comment: method for generation of random sequence not given.
Allocation concealment (selection bias)	Unclear risk	Comment: no information regarding concealment of randomization.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Quote: "The study group took a standard preparation of co‐trimoxazole, two tablets each containing trimethoprim 80 mg and sulphamethoxazole 400 mg twice daily for two days post‐cystoscopy. The control group received no antibiotics." Comment: participants in the control group were not administered antibiotic prophylaxis, while the treatment group receive tablets. Unlikely that participants and personnel were blinded to the intervention.
Blinding of outcome assessment (detection bias) Subjective outcomes	Unclear risk	Comment: systemic and localized symptoms after cystoscopy; adverse events not reported.
Blinding of outcome assessment (detection bias) Objective outcomes	Low risk	Comment: bacteriuria evaluated by urine culture was primary outcome. Result obtained from laboratory. Detection bias for this outcome was unlikely to be influenced by the unblinded design.
Incomplete outcome data (attrition bias) Systemic UTI	Unclear risk	Comment: outcome not reported.
Incomplete outcome data (attrition bias) Symptomatic UTI	Unclear risk	Comment: outcome not reported (bacteriuria was reported, but without differentiating whether participants had symptoms or not).
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	Comment: outcome not reported (bacteriuria was reported, but without differentiating whether participants had symptoms or not).
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.