Myocardial infarction: tPA is increasingly cost-effective in older patients.

The study

• Viewpoint: societal, but indirect costs such as time lost from work, and nonmedical costs were not included.
• Benefit assessment: cost-effectiveness ratios expressed as the additional lifetime costs required to add one extra year of life with tPA.
• Resources and costs: Costs of initial hospitalisation were calculated from the total cost estimates from the Duke Transition One cost-accounting system, and from Medicare diagnosis-related group (DRG) reimbursement rates. Costs ranged from $246 for cardioversion-defibrillation to $6236 for coronary bypass surgery. Costs of the thrombolytic agents were calculated from the Drug Topics Red Book average of 1993 wholesale prices (average of 1.5 million units of SK was $320; price for 100 mg tPA was $2,750), and from the average costs of the drugs in 16 randomly selected GUSTO hospitals (1.5 million units SK was $270; price for 100 mg tPA was $2,216). Physician's fees were taken from the Medicare fee schedule for North Carolina. All costs were expressed as 1993 dollars and discounted at 5% per year.
• Sensitivity analysis: survival and costs in both short and long term for the tPA group, costs and adverse health consequences of the increased risk of disabling stroke associated with tPA, and the utility weights we used to reflect the attitude of patients toward their current state of health were varied.

The evidence

intervention	cost
increase in cost and survival with tPA	$2, 845 ( increase in survival rate 11 per 1000 )
cost-effectiveness ratio of tPA	$32, 678 ( per life year saved )
cost-effectiveness ratio of tPA in inferior MI, age < or = 40	$203, 071 ( per life year saved )
cost-effectiveness ratio with tPA in anterior MI, age < or = 40	$123, 609 ( per life year saved )
ratio with tPA in inferior MI, age 41-60	$74, 816 ( per life year saved )
ratio with tPA in anterior MI, age 41-60	$49, 877 ( per life year saved )
ratio with tPA in inferior MI, age 61-75	$27, 873 ( per life year saved )
ratio with tPA in anterior MI, age 61-75	$20, 601 ( per life year saved )
ratio with tPA in inferior MI, age >75	$16, 246 ( per life year saved )
ratio with tPA in anterior MI, age >75	$13, 410 ( per life year saved )


Effect of sensitivity analysis: sensitivity analyses had no effect on the cost-effectiveness
• Quality weighting for life after MI (given by patients enrolled in the GUSTO study) was 0.9 (ie they would substitute 10 years of life 'like this' for 9 years in excellent health). To roughly convert the cost/year into cost/QALY, the values need to be divided by 0.9
• In the first 30 days after treatment in the GUSTO study, tPA produced a net increase of one disabling nonfatal stroke per 1000 patients treated, as compared with the rate with streptokinase.

Citation

1. Mark DB, Hlatky MA, Califf RM, et al: Cost effectiveness of thrombolytic therapy with tissue plasminogen activator as compared with streptokinase for acute myocardial infarction. New England Journal of Medicine 1995; 332 (21): 1418-1424
Contributor: Clare Wotton and Bob Phillips, February 2000
Reviewer:

_{Clinical Question.}

Patient	myocardial infarction
Intervention or Exposure	tissue plasminogen activator
Comparison	streptokinase
Outcome	cost-effectiveness