Aspirin versus warfarin in atrial fibrillation: decision analysis may help patients' choice.

Background: the primary prevention of ischaemic stroke in chronic non-valvular atrial fibrillation (AF) typically involves consideration of aspirin or warfarin. CHA(2)DS(2)-VASc estimates annual stroke rates for untreated AF patients, which are reduced by 60% with warfarin and by 20% with aspirin. HAS-BLED estimates annual rates of major bleeding on warfarin. The latter risk with aspirin is 0.5-1.2% per year.

Objective: given a 'warfarin, aspirin or no therapy' choice, AF patients will prefer the option that maximises the annual probability of not having a stroke and not having a major bleed.

Methods: decision tree applied to the 60 possible combinations of CHA(2)DS(2)-VASc and HAS-BLED scores.

Results: according to the pre-specified hypothesis, when CHA(2)DS(2)-VASc is <2, the balance of risk and benefit would advise no treatment; when CHA(2)DS(2)-VASc is 2 or 3, warfarin would be best when HAS-BLED <2, otherwise no treatment would be advised; for CHA(2)DS(2)-VASc =4, warfarin would be best when HAS-BLED <3, otherwise no treatment would be advised and for CHA(2)DS(2)-VASc ≥5, warfarin would be the preferred option if HAS-BLED <4, otherwise aspirin would be advised.

Conclusions: this theoretical exercise illustrates the potential benefit of decision analysis in an area where high complexity and uncertainty still remain.