The effects of apixaban compared with aspirin were consistent in those who previously failed and those who were expected to be unsuitable , for both SSE ( P interaction 0.13 ) and major bleeding ( P interaction 0.74 ) and were also consistent among different subgroups of patients who had previously failed VKA therapy defined by reasons for unsuitability , age , sex , renal function , CHADS2 score , aspirin dose , duration , indication , and quality of INR control of prior VKA use .