Sample size and power issues in estimating incremental cost-effectiveness ratios from clinical trials data.

It is becoming increasingly more common for a randomized controlled trial of a new therapy to include a prospective economic evaluation. The advantage of such trial-based cost-effectiveness is that conventional principles of statistical inference can be used to quantify uncertainty in the estimate of the incremental cost-effectiveness ratio (ICER). Numerous articles in the recent literature have outlined and compared various approaches for determining confidence intervals for the ICER. In this paper we address the issue of power and sample size in trial-based cost-effectiveness analysis. Our approach is to determine the required sample size to ensure that the resulting confidence interval is narrow enough to distinguish between two regions in the cost-effectiveness plane: one in which the new therapy is considered to be cost-effective and one in which it is not. As a result, for a given sample size, the cost-effectiveness plane is divided into two regions, separated by an ellipse centred at the origin, such that the sample size is adequate only if the truth lies on or outside the ellipse.

[1]  A Briggs,et al.  Uncertainty in the economic evaluation of health care technologies: the role of sensitivity analysis. , 1994, Health economics.

[2]  Erry,et al.  Cost effectiveness of thrombolytic therapy with tissue plasminogen activator as compared with streptokinase for acute myocardial infarction. , 1995, The New England journal of medicine.

[3]  R L Obenchain,et al.  Reporting cost-effectiveness analyses with confidence. , 1997, JAMA.

[4]  M J Al,et al.  Costs, effects and C/E-ratios alongside a clinical trial. , 1994, Health economics.

[5]  M. Weinstein,et al.  Clinical Decision Analysis , 1980 .

[6]  K. Schulman,et al.  Results of the Economic Evaluation of the FIRST Study: A Multinational Prospective Economic Evaluation , 1996, International Journal of Technology Assessment in Health Care.

[7]  Milton C. Weinstein,et al.  Recommendations for Reporting Cost-effectiveness Analyses , 1996 .

[8]  A A Stinnett,et al.  The negative side of cost-effectiveness analysis. , 1997, JAMA.

[9]  A S Detsky,et al.  How attractive does a new technology have to be to warrant adoption and utilization? Tentative guidelines for using clinical and economic evaluations. , 1992, CMAJ : Canadian Medical Association journal = journal de l'Association medicale canadienne.

[10]  M. Drummond,et al.  Users' guides to the medical literature. XIII. How to use an article on economic analysis of clinical practice. A. Are the results of the study valid? Evidence-Based Medicine Working Group. , 1997, JAMA.

[11]  Bernie J. O'Brien,et al.  In Search of Power and Significance: Issues in the Design and Analysis of Stochastic Cost-Effectiveness Studies in Health Care , 1994, Medical care.

[12]  M C Weinstein,et al.  Recommendations for reporting cost-effectiveness analyses. Panel on Cost-Effectiveness in Health and Medicine. , 1996, JAMA.

[13]  A R Willan,et al.  Confidence intervals for cost-effectiveness ratios: an application of Fieller's theorem. , 1996, Health economics.

[14]  M F Drummond,et al.  Users' guides to the medical literature. XIII. How to use an article on economic analysis of clinical practice. B. What are the results and will they help me in caring for my patients? Evidence-Based Medicine Working Group. , 1997, JAMA.

[15]  S. Stearns,et al.  Estimating confidence intervals for cost-effectiveness ratios: an example from a randomized trial. , 1996, Statistics in medicine.

[16]  M. Drummond,et al.  Health Care Technology: Effectiveness, Efficiency and Public Policy@@@Methods for the Economic Evaluation of Health Care Programmes , 1988 .

[17]  M F Drummond,et al.  Users' guides to the medical literature. XIII. How to use an article on economic analysis of clinical practice. A. Are the results of the study valid? Evidence-Based Medicine Working Group. , 1997, JAMA.

[18]  D. Osoba,et al.  Chemotherapy with mitoxantrone plus prednisone or prednisone alone for symptomatic hormone-resistant prostate cancer: a Canadian randomized trial with palliative end points. , 1996, Journal of clinical oncology : official journal of the American Society of Clinical Oncology.

[19]  G. Oster,et al.  Cholesterol-reduction intervention study (CRIS): a randomized trial to assess effectiveness and costs in clinical practice. , 1996, Archives of internal medicine.

[20]  A H Briggs,et al.  Pulling cost-effectiveness analysis up by its bootstraps: a non-parametric approach to confidence interval estimation. , 1997, Health economics.

[21]  A Gafni,et al.  Health care contingent valuation studies: a review and classification of the literature. , 1998, Health economics.

[22]  A R Willan,et al.  Power function arguments in support of an alternative approach for analyzing management trials. , 1994, Controlled clinical trials.

[23]  A H Briggs,et al.  Power and Sample Size Calculations for Stochastic Cost-Effectiveness Analysis , 1998, Medical decision making : an international journal of the Society for Medical Decision Making.

[24]  M C Weinstein,et al.  Use and misuse of the term "cost effective" in medicine. , 1986, The New England journal of medicine.

[25]  Amiram Gafni,et al.  When Do the "Dollars" Make Sense? , 1996, Medical decision making : an international journal of the Society for Medical Decision Making.

[26]  A A Stinnett,et al.  Net Health Benefits , 1998, Medical decision making : an international journal of the Society for Medical Decision Making.

[27]  Michael Drummond,et al.  Users' guides to the medical literature. XIII. How to use an article on economic analysis of clinical practice. B. What are the results and will they help me in caring for my patients? Evidence-Based Medicine Working Group. , 1997, JAMA.

[28]  P. Wakker,et al.  Confidence intervals for cost/effectiveness ratios. , 1995, Health economics.

[29]  A. Leaf,et al.  Cost effectiveness as a criterion for Medicare coverage. , 1989, The New England journal of medicine.

[30]  D Polsky,et al.  Confidence intervals for cost-effectiveness ratios: a comparison of four methods. , 1997, Health economics.