Table 38Summary strength of evidence and effect estimates: low-dose versus high-dose aspirin

Outcome and TimingSOEa and Effect Estimateb (95% CI)
Composite of all-cause mortality, nonfatal MI, or stroke at 6 monthsSOE = Insufficient (1 observational study; 20,469 patients)
Insufficient evidence due to CI that crosses 1: HR 0.92 (0.79 to 1.07)
Composite of all-cause mortality, nonfatal MI, or stroke at 1 yearSOE = Insufficient (2 observational studies; 31,186 patients)
Insufficient evidence due to inconsistency and imprecision: 1 study showed similar rates of composite events across 3 dosage categories for aspirin monotherapy and DAPT; the other study showed lower event rates when combining low-dose aspirin with ticagrelor and high-dose aspirin with clopidogrel
Composite of all-cause mortality, nonfatal MI, or revascularization at 1 yearSOE = Insufficient (3 observational studies; 9,249 patients)
Insufficient evidence due to imprecision: low-dose aspirin and high-dose aspirin had similar rates of ischemic events in all 3 studies
All-cause mortality at 6 monthsSOE = Insufficient (1 observational study; 20,469 patients)
Insufficient evidence due to imprecision: HR 0.89 (0.72 to 1.10)
All-cause mortality at 1 yearSOE = Insufficient (2 observational studies; 6,429 patients)
Insufficient evidence due to inconsistency and imprecision: 1 study (aspirin/clopidogrel) showed no difference between doses; the other found that high-dose aspirin (monotherapy) reduced mortality
Nonfatal MI at 6 monthsSOE = Low (1 observational study; 20,469 patients)
HR 0.79 (0.64 to 0.98); favors high-dose aspirin
Nonfatal MI at 1 yearSOE = Insufficient (1 observational study; 4,589 patients)
Insufficient evidence due to imprecision: HR 0.98 (0.66 to 1.48)
Stroke at 6 monthsSOE = Insufficient (1 observational study; 20,469 patients)
Insufficient evidence due to imprecision: HR 1.59 (0.95 to 2.65)
Stroke at 1 yearSOE = Insufficient (1 observational study; 4,589 patients)
Insufficient evidence due to imprecision: HR 1.37 (0.94 to 2.00)
Revascularization at 1 yearSOE = Insufficient (2 observational studies; 6,429 patients)
Insufficient evidence due to inconsistency and imprecision: 1 study (aspirin/clopidogrel) showed no difference between doses; the other study (aspirin monotherapy) showed more events with high dose
Major bleeding at 1 yearSOE = Low (3 observational studies; 19,971 patients)
1 study had high bleeding rates in low-dose group; 2 studies had high bleeding rates in high-dose group; favors low-dose aspirin

CI = confidence interval; DAPT = dual antiplatelet therapy; HR = hazard ratio; MI = myocardial infarction; SOE = strength of evidence

a

All SOE ratings of “Insufficient” (no evidence is available or available evidence is imprecise or too inconsistent to reach a conclusion) are shaded.

b

HRs less than 1 favor high-dose aspirin; HRs greater than 1 favor low-dose aspirin.

From: Discussion

Cover of Antiplatelet and Anticoagulant Treatments for Unstable Angina/Non–ST Elevation Myocardial Infarction
Antiplatelet and Anticoagulant Treatments for Unstable Angina/Non–ST Elevation Myocardial Infarction [Internet].
Comparative Effectiveness Reviews, No. 129.
Melloni C, Jones WS, Washam JB, et al.

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