Statistical reanalysis of vascular event outcomes in primary and secondary vascular prevention trials

Dual Antiplatelet Treatment up to 72 Hours after Ischemic Stroke

BACKGROUND

Dual antiplatelet treatment has been shown to lower the risk of recurrent stroke as compared with aspirin alone when treatment is initiated early (≤24 hours) after an acute mild stroke. The effect of clopidogrel plus aspirin as compared with aspirin alone administered within 72 hours after the onset of acute cerebral ischemia from atherosclerosis has not been well studied.

METHODS

In 222 hospitals in China, we conducted a double-blind, randomized, placebo-controlled, two-by-two factorial trial involving patients with mild ischemic stroke or high-risk transient ischemic attack (TIA) of presumed atherosclerotic cause who had not undergone thrombolysis or thrombectomy. Patients were randomly assigned, in a 1:1 ratio, within 72 hours after symptom onset to receive clopidogrel (300 mg on day 1 and 75 mg daily on days 2 to 90) plus aspirin (100 to 300 mg on day 1 and 100 mg daily on days 2 to 21) or matching clopidogrel placebo plus aspirin (100 to 300 mg on day 1 and 100 mg daily on days 2 to 90). There was no interaction between this component of the factorial trial design and a second part that compared immediate with delayed statin treatment (not reported here). The primary efficacy outcome was new stroke, and the primary safety outcome was moderate-to-severe bleeding - both assessed within 90 days.

RESULTS

A total of 6100 patients were enrolled, with 3050 assigned to each trial group. TIA was the qualifying event for enrollment in 13.1% of the patients. A total of 12.8% of the patients were assigned to a treatment group no more than 24 hours after stroke onset, and 87.2% were assigned after 24 hours and no more than 72 hours after stroke onset. A new stroke occurred in 222 patients (7.3%) in the clopidogrel-aspirin group and in 279 (9.2%) in the aspirin group (hazard ratio, 0.79; 95% confidence interval [CI], 0.66 to 0.94; P = 0.008). Moderate-to-severe bleeding occurred in 27 patients (0.9%) in the clopidogrel-aspirin group and in 13 (0.4%) in the aspirin group (hazard ratio, 2.08; 95% CI, 1.07 to 4.04; P = 0.03).

CONCLUSIONS

Among patients with mild ischemic stroke or high-risk TIA of presumed atherosclerotic cause, combined clopidogrel-aspirin therapy initiated within 72 hours after stroke onset led to a lower risk of new stroke at 90 days than aspirin therapy alone but was associated with a low but higher risk of moderate-to-severe bleeding. (Funded by the National Natural Science Foundation of China and others; INSPIRES ClinicalTrials.gov number, NCT03635749.).

Optimising the analysis of vascular prevention trials: Re-Assessment of the TARDIS trial, the first prevention trial to adopt an ordinal primary outcome measure

Background

Ordinalised vascular outcomes incorporating event severity are more informative than binary outcomes that just include event numbers. The TARDIS trial was the first vascular prevention study to use an ordinalised vascular outcome as its primary efficacy and safety measures and collected severity information for other vascular events.

Methods

TARDIS was an international prospective randomised open-label blinded-endpoint trial assessing one month of intensive versus guideline antiplatelet therapy in patients with acute non-cardioembolic stroke or TIA. Vascular events and their severity were recorded up to final follow-up at 90 days post randomisation. For each outcome, statistical techniques compared ordinal/continuous (10 models) and dichotomous (5 models) analyses; results were then ranked with the smallest p-value being given the smallest rank. Outcomes were also assessed within the pre-defined subgroup of participants with mild stroke (NIHSS≤3), or TIA recruited within 24 h.

Results

Ordinal versions of vascular event outcomes were created in 3096 participants for stroke, myocardial infarction, major cardiac events, bleeding events, serious adverse events and venous thromboembolism (VTE), with 32 outcomes being created overall (29 in the subgroup population due to the absence of VTE events). Overall, the tests run on ordinal outcomes tended to rank higher than tests performed on binary outcomes. 764 (24.7%) participants were recruited within 24 h of a mild stroke/TIA; again, tests run on ordinal outcomes ranked higher.

Conclusions

In TARDIS, tests performed on ordinal vascular outcomes tended to attain a higher rank than those performed on binary outcomes.

Trial registration

ISRCTN47823388.

Bleeding with intensive versus guideline antiplatelet therapy in acute cerebral ischaemia

Intensive antiplatelet therapy did not reduce recurrent stroke/transient ischaemic attack (TIA) events as compared with guideline treatment in the Triple Antiplatelets for Reducing Dependency after Ischaemic Stroke (TARDIS) trial, but did increase the frequency and severity of bleeding. In this pre-specified analysis, we investigated predictors of bleeding and the association of bleeding with outcome. TARDIS was an international prospective randomised open-label blinded-endpoint trial in participants with ischaemic stroke or TIA within 48 h of onset. Participants were randomised to 30 days of intensive antiplatelet therapy (aspirin, clopidogrel, dipyridamole) or guideline-based therapy (either clopidogrel alone or combined aspirin and dipyridamole). Bleeding was defined using the International Society on Thrombosis and Haemostasis five-level ordered categorical scale: fatal, major, moderate, minor, none. Of 3,096 participants, bleeding severity was: fatal 0.4%, major 1.5%, moderate 1.2%, minor 11.4%, none 85.5%. Major/fatal bleeding was increased with intensive as compared with guideline therapy: 39 vs. 17 participants, adjusted hazard ratio 2.21, 95% CI 1.24-3.93, p = 0.007. Bleeding events diverged between treatment groups in the 8-35 day period but not in the 0-7 or 36-90 day epochs. In multivariate analysis more, and more severe, bleeding events were seen with increasing age, female sex, pre-morbid dependency, increased time to randomisation, prior major bleed, prior antiplatelet therapy and in those randomised to triple vs guideline antiplatelet therapy. More severe bleeding was associated with worse clinical outcomes across multiple physical, emotional and quality of life domains.Trial registration ISRCTN47823388 .

Rationale and design of a randomised double-blind 2×2 factorial trial comparing the effect of a 3-month intensive statin and antiplatelet therapy for patients with acute mild ischaemic stroke or high-risk TIA with intracranial or extracranial atherosclerosis (INSPIRES)

BACKGROUND

It remains unclear if intensive antiplatelet and statin treatments begun within 24-72 hours of cerebral ischaemic events from intracranial or extracranial atherosclerosis is effective or safe.

METHODS

The Intensive Statin and Antiplatelet Therapy for High-risk Intracranial or Extracranial Atherosclerosis (INSPIRES) trial is a randomised, double-blind, placebo-controlled, multicentre and 2×2 factorial trial. 6100 individuals between the ages of 35 and 80 who have experienced a mild ischaemic stroke or high-risk transient ischaemic attack (TIA) within the previous 72 hours that is attributed to ≥50% atherosclerotic stenosis of a major intracranial or extracranial artery or multiple infarctions of atherosclerotic origin will be enrolled in the trial. Eligible subjects will be randomised 1:1:1:1 to one of four groups: (1) intensive antiplatelet therapy (combined clopidogrel and aspirin for days 1-21, then aspirin placebo and clopidogrel for days 22-90) plus immediate intensive statin therapy(atorvastatin at a dose of 80 mg daily for the first 21 days, then 40 mg daily for days 22-90); (2) intensive antiplatelet therapy plus delayed intensive statin therapy (atorvastatin placebo for days 1-3, followed by 40 mg per day of atorvastatin for days 4-90); (3) standard antiplatelet therapy (combination of clopidogrel placebo with aspirin for 90 days) plus immediate intensive statin therapy and (4) standard antiplatelet therapy plus delayed intensive statin therapy. The primary efficacy endpoint is any new stroke (ischaemic or haemorrhagic) within 90 days after randomisation. The primary safety endpoint is moderate to severe bleeding at 90 days.

CONCLUSION

The INSPIRES trial will assess the efficacy and safety of intensive antiplatelet therapy and immediate intensive statin therapy begun within 72 hours of onset in decreasing the recurrent stroke at 90 days in patients with acute mild ischaemic stroke or high-risk TIA of intracranial or extracranial atherosclerosis origin.

TRIAL REGISTRATION NUMBER

NCT03635749.