RISC 1990.

Study characteristics
Methods	Prospective, randomized, double‐blind, placebo‐controlled multicenter trial.
Participants	796 patients (<70 years old) with unstable angina or NSTEMI. Chest pain occurring within previous 4 weeks (randomized to treatment up to 72 hours after admission).
Interventions	4 treatment groups, Group 1: ASA placebo + UFH placebo Group 2: ASA placebo + UFH 5000 U IV 6 hourly x 1 day, then 3750 IV 6 hourly x 4 days Group 3: ASA 75 mg/d + UFH placebo (n = 189) Group 4: ASA 75 mg/d + UFH (same as group 2) (n = 210)
Outcomes	Outcomes at 5 days, 30 days and 90 days. Primary outcome: Death or MI (90 days), revascularization,
Notes	Only used data from groups 3 and 4.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Insufficient information about the sequence generation process
Allocation concealment (selection bias)	Unclear risk	Method of concealment not described. Probably not done.
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Trial labeled as “double‐blind” but the study did not address this further
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	The study did not address this outcome
Incomplete outcome data (attrition bias) All outcomes	Low risk	Missing outcome data balanced in numbers across groups. Quote: “After 3 months, 95% of patients remained on treatment with no difference between the aspirin and placebo groups”
Selective reporting (reporting bias)	Low risk	No protocol available, all expected outcomes reported.
Other bias	Low risk	Early conclusion of the study recommended by the safety committee, the follow‐up was planned for 1 year (it was reduced to 3 months), probably not a risk of bias for this