Andrassy 1974.

Methods	Study design: randomised, double‐blind clinical trial
Participants	Country: Germany No. of participants: 92 Age: not stated Gender: M = 50, F = 42 Inclusion criteria: end‐stage renal failure Exclusion criteria: not stated
Interventions	Treatment: aspirin 500 mg daily (n = 45) Control: placebo (n = 47) Duration: started 1 day pre‐operatively and continued for 28 days
Outcomes	Primary: fistula thrombosis, 28 days follow‐up
Notes	Brescia‐Cimino fistula formation
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Independent statistician used but exact method not stated
Allocation concealment (selection bias)	Unclear risk	No pre‐allocation bias
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Insufficient information provided to assess
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Assessor not stated
Incomplete outcome data (attrition bias) All outcomes	Low risk	No missing data
Selective reporting (reporting bias)	Unclear risk	Pre‐study protocol not available
Other bias	Low risk	Nil obvious