Reporting the cost-effectiveness of interventions with nonsignificant effect differences: example from a trial of secondary prevention of coronary heart disease.

OBJECTIVES: This study reports the cost-effectiveness of interventions with nonsignificant differences in effect, and considers reporting of cost-effectiveness in situations where nonsignificant differences arise in some but not all end points. METHODS: Data on costs and effects associated with three end points (adequate assessment, risk factors, and life-years) were derived from a trial of methods to promote secondary prevention of coronary heart disease. Incremental cost per life-year gained figures were calculated, and the uncertainty around these was displayed on cost-effectiveness planes in the form of ellipses. RESULTS: There was a significant difference in one of the intermediate end points (adequate assessment) but nonsignificant differences in the other intermediate end point (risk factors) and the final end point (life-years). Estimation of cost per life-year figures revealed the cost-effectiveness of the interventions to be unfavorable. CONCLUSIONS: Cost-effectiveness ratios based on final end points should be calculated even in situations where nonsignificant differences in life-years arise, to avoid publication bias and to provide decision makers with useful information. Uncertainty in the incremental cost-effectiveness ratios should be estimated and presented graphically.