CAST 1997.

Study characteristics
Methods	Concealment: centrally produced, prepacked, sequentially numbered envelopes Exclusions during trial: 0 Losses to follow‐up: 451 (219 treatment, 232 control) at 4 weeks
Participants	China 21,106 participants 63% male 28% aged > 70 years 87% had CT before entry Ischaemic stroke < 48 hours since stroke onset
Interventions	Treatment: aspirin 160 mg once daily orally or via nasogastric tube Control: placebo Duration: 4 weeks, or until death or earlier discharge
Outcomes	Death Recurrent stroke Functional outcome (mRS < 3 = independent) Pulmonary embolism (symptomatic) Extracranial haemorrhage
Funding source	Medical Research Council supported the Clinical Trial Service Unit, Oxford. Trial tablets donated by Shandong Xinhua Pharmaceuticals.
Notes	Exclusions not specified by protocol but by responsible physician, possibly including increased risk of adverse effects, or little likelihood of any worthwhile benefit in hospital. Follow‐up: 4 weeks.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Random component in the sequence generation described.
Allocation concealment (selection bias)	Low risk	Sequentially numbered envelopes used.
Blinding of participants and personnel (performance bias) all outcomes	Unclear risk	Unclear whether there was blinding of participants and personnel.
Blinding of outcome assessment (detection bias) all outcomes	Unclear risk	Unclear whether there was blinding of outcome assessment.
Incomplete outcome data (attrition bias) all outcomes	Low risk	Missing outcome data balanced in numbers across intervention groups.
Selective reporting (reporting bias)	Low risk	Study protocol available.
Other bias	Low risk	No other sources of bias identified.