The results from this cost-effectiveness analysis become even more dramatic when applied to the Canadian population. Using 1991 census data (the most recently available), a net savings to the health care system is realized when warfarin is used on indicated people. Up to 1.25% major complication rate will still result in a net savings (Tables 8-10). Similar results were also found in a Swedish study, indicating a net savings up to a 1.3% major bleeding complication rate. The critical value here is the rate of major bleeding which increases with age. buy flovent inhaler
The paiients in this meta-analysis were, on average, 70 years old. Patients 60 years of age and younger are considered to be at low risk for stroke and are generally not prescribed warfarin treatment. Other low risk individuals include those with lone atrial fibrillation and, perhaps more controversially, paroxysmal atrial fibrillation.
Population statistics for Canada
|Age||Total population*||Prevalence of atrial fibrillation^: n (%)||Eligible for warfarin*|
*Census Canada 1991; fFramingham study (9); *Swedish study -50% eligibility except for 70- to 79-year-olds (only 30% eligible) (13); §Too high risk of bleeding (13)
Potential total reduction of cardiovascular events* in Canada using warfarin
|Stroke rateNo antithrombotic therapy @4.||35%||Num||ber o||f strok2058||ies*|
|Number of strokes prevented||1348|
|Major hemorrhage (%):||0.3||0.83||1.0||1.1||1.25||1.3|
|Number of hemorrhages:||142||393||473||520||591||615|
*Includes stroke and major bleed; fStroke rate is multiplied by warfarin eligible group (n=47,307); *Number of strokes prevented minus number of hemorrhages
Net saving (cost) with warfarin therapy
|Hemorrhage(%)0.3||# of people treated to prevent one stroke*39||Cost of treatment*$17,271.93||Savings*$10,228.07|
*Reciprocal of reduction in rate of stroke;fNumber of people treated to prevent one stroke x cost of warfarin therapy; *Cost of stroke minus cost of warfarin treatment
Assessing the question of risk/ benefit is a formidable task. Some have suggested, using decision analysis, that the risk of bleeding must be at least six times more detrimental than emboli to justify withholding of anticoagulation. This analysis found major bleeding events to be fewer then embolic events (0.94% and 1.50%, respectively, in the warfarin group). However, when minor bleeding events are compared with embolic events, there is a 7.2-fold increase (10.85% ver sus 1.50%, respectively, in the warfarin group) in bleeding. This comparison may not be valid since minor bleeding events, as the name suggests, are not life threatening compared with the seriousness of an embolic event.