SF-6D and EQ-5D result in widely divergent incremental cost-effectiveness ratios in a clinical trial of older women: implications for health policy decisions

Abstract

Summary: Using two instruments (SF-6D and EQ-5D) to estimate quality adjusted life years (QALYs), we conducted an economic evaluation of a 12-month randomized controlled trial with a 12-month follow-up study in older women to evaluate the value for money of two doses of resistance training compared with balance and tone classes. We found that the incremental QALYs estimated from the SF-6D were two- to threefold greater than those estimated from the EQ-5D.

Introduction: Decision makers must continually choose between existing and new interventions. Hence, economic evaluations are increasingly prevalent. The impact of quality-adjusted life year (QALY) estimates using different instruments on the incremental cost-effectiveness ratios (ICERs) is not well understood in older adults. Thus, we compared ICERs, in older women, estimated by the EuroQol-5D (EQ-5D) and the Short Form-6D (SF-6D) to discuss implications on decision making.

Methods: Using both the EQ-5D and the SF-6D, we compared the incremental cost per QALY gained in a randomized controlled trial of resistance training in 155 community-dwelling women aged 65 to 75 years. The 12-month randomized controlled trial included a subsequent 12-month follow-up. Our focus, the follow-up study, included 123 of the 155 participants from the Brain Power study; 98 took part in the economic evaluation (twice-weekly balance and tone exercises, n = 28; once-weekly resistance training, n = 35; twice-weekly resistance training, n = 35). Our primary outcome measure was the incremental cost per QALY gained of once- or twice-weekly resistance training compared with balance and tone exercises.

Results: At cessation of the follow-up study, the incremental QALY was -0.051 (EQ-5D) and -0.144 (SF-6D) for the once-weekly resistance training group and -0.081 (EQ-5D) and -0.127 (SF-6D) for the twice-weekly resistance training group compared with balance and tone classes.

Conclusion: The incremental QALYs estimated from the SF-6D were two- to threefold greater than those estimated from the EQ-5D. Given the large magnitude of difference, the choice of preference-based utility instrument may substantially impact health care decisions.

Figure 1a

1a) Cost effective plane depicting the 95% confidence ellipses of incremental cost and effectiveness for comparison between twice weekly resistance training (2RT) and twice weekly balance and tone (2BT, comparator); 1b) Cost effective plane depicting the 95% confidence ellipses of incremental cost and effectiveness for comparison between once weekly resistance training (1RT) and twice weekly balance and tone (2BT, comparator). QALY estimates are based on utility scores from the EQ-5D. QALY estimates are based on utility score from the SF-6D for figures 1a and 1b. 1c) Cost effective plane depicting the 95% confidence ellipses of incremental cost and effectiveness for comparison between twice weekly resistance training (2RT) and twice weekly balance and tone (2BT, comparator); 1d) Cost effective plane depicting the 95% confidence ellipses of incremental cost and effectiveness for comparison between once weekly resistance training (1RT) and twice weekly balance and tone (2BT, comparator). QALY estimates are based on utility scores from the EQ-5D for figures 1c and 1d.

Figure

1a. Cost effective plane depicting the 95% confidence ellipses of incremental cost and effectiveness for comparison between once-weekly resistance training and balance and tone (comparator) with Quality Adjusted Life Years (QALYs) estimated from the EuroQol (EQ-5D); 1b. Cost effective plane depicting the 95% confidence ellipses of incremental cost and effectiveness for comparison between twice-weekly resistance training and balance and tone (comparator) with QALYs estimated from the EQ-5D.