Purpose: The purpose of this study was to compare methods of analyzing cost-effectiveness data from nonrandomized atrial fibrillation (AF) patients treated with rhythm control or rate control strategies.
Method: Patients were enrolled from 532 sites in 21 countries between May 2007 and April 2008 in the Registry on Cardiac Rhythm Disorders (RECORD AF). Hospitalizations, complications and cardiovascular events were assigned a Diagnosis Related Group (DRG) and costs estimated by multiplying the relative weight of a DRG by the Medicare base rate in 2008 ($4,893). Outpatient procedures were assigned a CPT4 code for costing, and Redbook 2007 average wholesale price (AWP) was used to cost medications. Lifetime costs were estimated using average Medicare participant per capita expenditure in 2008 ($6,458). Quality adjusted life years (QALYs) were calculated by estimating life expectancy based on Framingham data and multiplying by utility scores from the EQ-5D. Propensity scores were calculated from demographic and clinical history information. Rhythm and control patients were matched on propensity scores by use of a greedy matching algorithm. Stabilized inverse probability weighting (IPW) was used to weight both costs and life expectancies. Bootstrap analysis was used to compare costs and estimate incremental cost-effectiveness ratios (ICER). Lifetime costs and life expectancy were discounted 3%.
Result: Observed data indicated rhythm is cost-effective with 100% of bootstrap replicates in quadrant 1 of the cost-effectiveness plane. Propensity score matching indicated similar costs and QALYs of the therapies, but only 57% of patients were matched. IPW analysis indicated rhythm control to be cost-effective with ICER of $3,977, and probability of 0.87 of the ICER < $30,000.
Conclusion: Differences between rhythm control and rate control strategies with respect to total lifetime cost and QALYs were small in the matched (< $140 and < 0.1 for cost and QALYs respectively) and IPW (< $571 and 0.15) analyses, and were in the direction of cost-effectiveness of rhythm – more expensive, but more effective. Results for the observed data were similar and indicated rhythm was cost-effective. From an economic standpoint the differences in results were small. From a methodological standpoint, the potential confounding in nonrandomized studies may give misleading results. Propensity score matching may result in a severe loss of data, whereas IPW analysis allows the use of all available data.