Nielsen 2000.

Methods	RCT, single‐centre, parallel study
Participants	Total number of randomized participants: 55 Inclusion criteria Male patients on low‐dose acetylsalicylic acid therapy (150 mg to 300 mg) with obstructive symptoms, and clinical and laboratory evidence suggestive of benign or malignant prostatic enlargement Exclusion criteria Undergoing treatment with anticoagulants, and other NSAIDs Recent (within 6 months) myocardial infarction Unstable angina Stroke Transient cerebral ischaemia History of bleeding diathesis Serum creatinine > 200 mmol/L Arterial hypertension with blood pressure > 220/120 mmHg Type of surgery TURP Baseline characteristics Continuation group Age, median (IQR): 70 (66 to 74) years Gender: all male participants BMI, mean (SD): not reported Severity of illness: not reported Type of anaesthesia, n: SPA: all participants Participants with coronary stent, n: not reported Reason for having antiplatelet therapy: not reported Type of antiplatelet therapy prior to study: 150 mg to 300 mg aspirin Duration of antiplatelet therapy prior to study: not reported Discontinuation group Age, median (IQR): 69 (65 to 76) years Gender: all male participants BMI, mean (SD): not reported Severity of illness score: not reported Type of anaesthesia, n: SPA: all participants Participants with coronary stent, n: not reported Reason for having antiplatelet therapy: not reported Type of antiplatelet therapy prior to study: 150 to 300 mg aspirin Duration of antiplatelet therapy prior to study: not reported Country: Denmark Setting: hospital
Interventions	Continuation group Number of analysed participants = 26 (study authors report 2 losses after randomization but do not report total number of randomized participants in each group) Details: usual dose of aspirin was discontinued 10 days before surgery and participant given 150 mg aspirin. Participants resumed usual dose after catheter removal Discontinuation group Number of analysed participants = 27 (study authors report 2 losses after randomization but do not report total number of randomized participants in each group) Details: usual antiplatelet therapy discontinued 10 days prior to study and participant given placebo. Participants resumed usual antiplatelet therapy after catheter removal
Outcomes	Intra‐operative and postoperative blood loss Transfusion requirements Re‐operation due to blood loss Myocardial infarction Mortality Secondary haemorrhage Length of hospital stay Median time to catheter removal Histology
Notes	Funding/declarations of interest: Leo Pharmaceutical Products, Ballerup, Denmark. Donated medication Study dates: not reported
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Stated as randomized but no additional details describing random sequence generation were provided in the published study report
Allocation concealment (selection bias)	Unclear risk	Allocation list was kept at the pharmaceutical company which provided the drugs. No additional details
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Stated as double‐blind and placebo was used to blind the participants. We assumed that personnel were also blinded to group allocation
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	No details describing blinding of outcome assessment were provided in the published study report
Incomplete outcome data (attrition bias) All outcomes	Low risk	Two losses from each group. Study authors do not report to which group these participants belonged. However, few losses and unlikely to influence outcome data
Selective reporting (reporting bias)	Unclear risk	Clinical trial registration or prospectively published protocol not reported. Not feasible to assess risk of selective reporting bias
Other bias	Unclear risk	Study is supported by pharmaceutical company. Study authors do not report level of involvement in trial design and management by the company. Baseline characteristics not reported