INCREMENTAL COST EFFECTIVENESS RATIOS AND CONFIDENCE INTERVALS -- RELATIONSHIP OF CALCULATIONS WITH NNT VERSUS BOOTSTRAP METHODS

Author(s)

McGhan W1, Peterson A1, Kulkarni S2, Kamble S1, Shetty N1, 1University of the Sciences, Philadelphia, PA, USA; 2Fox Chase Cancer Center, Cheltenham, PA, USA

The concept of incremental cost effectiveness ratios (ICERs) and confidence intervals (CIs) may seem complicated to many practitioners and decision makers. There is a growing body of literature regarding the use of NNT (number needed to treat) as a statistic that may be easier to understand in clinical practice. NNTs and ICERs are receiving increased attention in the interface of clinical and economic concepts. OBJECTIVE: To compare the ICER and CI results by using NNT-related calculations versus bootstrap analyses utilizing datasets from three published papers. METHODS: An NNT spreadsheet calculator was developed that generates NNT confidence intervals and incremental cost to treat calculations. Datasets with an aggregate total of over 2000 patients from three previously published pharmacoeconomic studies were analyzed with both the NNT and bootstrap ICER approach. The NNT calculator used a two by two contingency table with additional cells for including cost of each treatment. Confidence intervals (95%) were calculated for NNT and the upper and lower values of the incremental cost per successfully treated patient. In contrast, the bootstrap software utilizes each individual patient case in the datasets to generate ICER ratios and ICER confidence intervals. RESULTS: The NNT results for the mean cost needed to treat for one successful outcome showed good agreement with the bootstrap generated ICER slopes. For NNT versus bootstrap, the anti-platelet study mean ICERs were $43,729 vs. $43,742, the antidepressant comparative study ICERs were -$1648 vs -$1647 and the antidepressant combination study ICERs were -$188,014 vs. -$188,012. Using 5th and 95th percentiles for cost of treatment multiplied by corresponding NNT confidence intervals did not generate very close agreement with the bootstrapped CIs. CONCLUSIONS: NNT related calculations may be a method for initially analyzing local pilot data or explore the economic ramifications of a clinical publication when the full dataset is not available.

Conference/Value in Health Info

2004-05, ISPOR 2004, Arlington, VA, USA

Value in Health, Vol. 7, No. 3 (May/June 2004)

Code

PMD3

Topic

Economic Evaluation

Topic Subcategory

Cost/Cost of Illness/Resource Use Studies

Disease

Multiple Diseases

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