Table 5 presents a summary of the deterministic results. The results show that the strategy that uses first generation endometrial ablation as the first intervention of the pathway is dominated by all the other strategies as it is both more expensive and less effective in terms of producing QALYs. The strategy that adopts hysterectomy as the first and only intervention produces the most QALYs. In comparison with the strategy that uses Mirena first, hysterectomy is more expensive but generates more QALYs. The incremental cost effectiveness ratio (ICER) representing the value of the additional benefit of the hysterectomy strategy compared with Mirena is £1440 (€1633, $2350) per additional QALY. The hysterectomy strategy also produces more QALYs than the second generation endometrial ablation strategy and the estimated incremental cost effectiveness ratio for this comparison is £970 per additional QALY.
Table 5 Summary of deterministic base case, subgroup, and sensitivity analyses of model to determine cost effectiveness of different treatments for heavy menstrual bleeding
The Mirena strategy dominates the first generation endometrial ablation strategy, being cheaper and more effective in producing QALYs. But though it is also cheaper than second generation endometrial ablation, in this comparison it produces fewer QALYs. The incremental cost effectiveness ratio for the second generation endometrial ablation versus Mirena is £2980 per additional QALY.
Figure 2 shows the result of the probabilistic sensitivity analysis. Detailed interpretation of this analysis and additional value of information analysis is presented elsewhere.6
Briefly, it shows the probability that the preferred option is cost effective for any given threshold incremental cost effectiveness ratio for all but a few replications—and the few account for a negligible probability. Mirena was the least costly option and, for low acceptable threshold incremental cost effectiveness ratios, Mirena is preferred with certainty within this model given its assumptions. But as the threshold incremental cost effectiveness ratio increases hysterectomy becomes the preferred option.
Fig 2 Cost effectiveness acceptability frontier, showing probability that preferred option is cost effective (ICER=incremental cost effectiveness ratio)
In some replications of the model (accounting for 20% of the probability), hysterectomy was not the most effective option (in terms of total number of QALYs). At an incremental cost effectiveness ratio of £1440, the preferred option changes from Mirena to hysterectomy, so there is a discontinuity in the cost effectiveness acceptability curve.
In the subgroup analysis, carried out to explore the impact of the length of the uterine cavity on cost effectiveness of the alternative interventions for heavy menstrual bleeding, we carried out two separate analyses and a corresponding probabilistic sensitivity analysis. The results of the subgroup analysis showed a small effect of shorter and longer uterine cavity length, which was in the same direction for both. For both cases the results moved slightly so that first generation ablation was no longer “dominated” by hysterectomy and the incremental cost per additional QALY of hysterectomy compared with other strategies was slightly higher (less favourable) than in the base case. There is, however, unlikely to be a change in the decision based on these results and hysterectomy remains the preferred strategy. The results of the probabilistic sensitivity analysis reinforced the results of this deterministic subgroup analysis and are not presented.
In a further deterministic sensitivity analysis, we changed the utilities from the base case in which the mean utility values are used, to reported median values. In the first deterministic sensitivity analysis we used the “median” quality of life values from Sculpher20
and assumed the quality of life scores as a result of first and second generation ablation were equal based on median values (well after first or second generation endometrial ablation 0.90). The key change in results compared with the base case is that there is a clear shift away from the hysterectomy strategy in favour of second generation endometrial ablation. This dominates first generation endometrial ablation as before, but now also dominates hysterectomy. Meanwhile, in this sensitivity analysis the incremental cost effectiveness ratio for second generation endometrial ablation versus the Mirena strategy was £1000 per additional QALY.
The results of the second deterministic sensitivity analysis are similar to those presented in the first. Once again the strategy of second generation endometrial ablation dominates first generation endometrial ablation and hysterectomy, in contrast with the base case. The incremental cost effectiveness ratio for second generation endometrial ablation versus Mirena is £3624 per additional QALY.
Figures 3 and 4 summarise and compare the key findings from changing the utility values (presented in the first and second sensitivity analyses) with the base case . Figure 3 shows that with baseline (mean) utilities, Mirena is the least costly strategy and hysterectomy the most effective. The strategy that starts with first generation endometrial ablation is simply dominated by all of the other strategies. The strategy that starts with second generation endometrial ablation is excluded by extended dominance between Mirena and hysterectomy.
Fig 3 Base case deterministic results of cost effectiveness of different treatments for heavy menstrual bleeding (Mirena, hysterectomy, and first and second generation ablation techniques)
Fig 4 Deterministic sensitivity analysis with median utility values instead of means for cost effectiveness of different treatments for heavy menstrual bleeding (Mirena, hysterectomy, and first and second generation ablation techniques)
Figure 4 shows the same costs for all strategies as figure 3 but the total QALYs are increased. By using the median utility values, second generation ablation now becomes the most effective strategy: both first generation endometrial ablation and hysterectomy are simply dominated by second generation endometrial ablation.