This section presents the results of the base-case analysis for the deterministic and probabilistic models. These analyses set out the most plausible estimates of cost-effectiveness, given the limited evidence available and taking the results of the IPD meta-analysis at face value. As described in Chapter 7, Long-term treatment effect, there is significant uncertainty about the long-term benefits of early intensive ABA-based interventions. Therefore, two scenarios are presented in the base-case analysis: an optimistic scenario, in which the comparative advantage of early intensive ABA-based interventions are assumed to persist throughout the time horizon of the model, and a pessimistic scenario, in which the treatment effect dissipates to zero.
Deterministic results
Initial results are presented assuming a narrow health-care perspective and therefore only costs and benefits accruing to the health-care system are included. Results of this analysis are presented in Table 20. Full results with a break down of costs are presented in Appendix 19.
In the pessimistic scenario, early intensive ABA-based interventions are associated with £57,879 in additional costs and generates 0.24 additional QALYs. The resulting ICER is £236,837 per additional QALY. In the optimistic scenario, early intensive ABA-based interventions are associated with £57,233 in additional costs and generates 0.84 additional QALYs. The resulting ICER is £68,362 per additional QALY. Using NICE decision rules to benchmark the results of the cost-effectiveness analysis and adopting a £30,000 per QALY threshold, these results indicate that for early intensive ABA-based interventions to be considered cost-effective in the pessimistic scenario, it would be necessary for there to be a further 1.68 QALYs or £50,547 in additional cost savings not captured by the economic model. In the optimistic scenario, early intensive ABA-based interventions would be cost-effective at a threshold of £30,000 per QALY if there were a further 1.07 QALYs or £32,117 in additional cost savings not captured by the model.
A comparison of the incremental costs in the pessimistic and optimistic scenarios shows only a relatively small difference. This reflects the lack of scope for early intensive ABA-based interventions to generate significant cost savings in the health service sector. This similarity in incremental costs, however, contrasts with a comparison of health benefits produced, which are significantly larger in the optimistic scenario. Building on this initial scenario, Table 21 presents results considering a wider public sector perspective.
TABLE 20 Base-case results: NHS and social services perspective
Scenario Therapy Cost (£) QALYs Incremental cost (£) Incremental QALYs ICER (£)
Pessimistic ABA 76,622 4.61 57,879 0.24 236,837 TAU/eclectic 18,743 4.37
Optimistic ABA 75,976 5.21 57,233 0.84 68,362 TAU/eclectic 18,743 4.37
In the pessimistic scenario, early intensive ABA-based interventions are associated with £43,940 in additional costs and generates 0.24 additional QALYs. The resulting estimated ICER is £179,799 per additional QALY. In the optimistic scenario, early intensive ABA-based interventions are associated with £36,242 in additional costs and generates 0.84 additional QALYs. The resulting estimated ICER is £43,289 per additional QALY. The adoption of a public sector perspective has a significant impact on incremental costs in both the pessimistic and optimistic scenarios, with incremental costs falling by £13,939 and £20,991, respectively. This is because improvements in cognitive ability and adaptive behaviour could have a large impact in public sector cost savings, which are predominantly caused by changes in education placement.
These differences in incremental costs have a significant impact on the resulting ICER, which fall appreciably in both the pessimistic and optimistic scenarios. However, in both scenarios they remain firmly above the NICE threshold of £20,000–30,000 per QALY. Assuming a threshold of £30,000 per QALY, and making pessimistic assumptions about the long-term treatment effect, it would be necessary for early intensive ABA-based interventions to generate either a further 1.22 QALYs worth of additional health or non-health benefits, or a further £36,608 in additional costs savings. In the optimistic scenario these fall to either a 0.37 QALYs worth of benefits or £11,126 in cost savings.
Probabilistic results
A probabilistic sensitivity analysis was conducted to account for the effects of parameter uncertainty and cost-effectiveness acceptability generated. The base-case results for the probabilistic model are shown in Table 22.
The results of the probabilistic analysis broadly correspond with those of the deterministic analysis and indicate that further health or non-health benefits or cost savings would need to be generated for early intensive ABA-based interventions to be cost-effective at a threshold of £30,000 per QALY. Assuming a
TABLE 21 Base-case results: public sector perspective
Scenario Therapy Cost (£) QALYs Incremental cost (£) Incremental QALYs ICER (£)
Pessimistic ABA 195,310 4.61 43,940 0.24 179,799 TAU/eclectic 151,370 4.37
Optimistic ABA 187,612 5.21 36,242 0.84 43,289 TAU/eclectic 151,370 4.37
TABLE 22 Base-case results: probabilistic analysis
Scenario Therapy Cost (£) QALYs Incremental cost (£) Incremental QALYs ICER (£)
NHS and social services perspective
Pessimistic ABA 76,587 5.02 58,940 0.24 240,868 TAU/eclectic 17,648 4.77
Optimistic ABA 76,341 5.60 58,630 0.85 69,385 TAU/eclectic 17,711 4.75
Public sector perspective
Pessimistic ABA 191,264 5.00 46,103 0.24 189,122 TAU/eclectic 145,161 4.75
Optimistic ABA 184,411 5.61 39,233 0.84 46,768 TAU/eclectic 145,178 4.77
COST-EFFECTIVENESS AND BUDGET IMPACT RESULTS
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public sector perspective, in the pessimistic scenario it would be necessary for early intensive ABA-based interventions to generate either a further 1.29 additional QALYs or produce £38,790 in additional cost savings. In the optimistic scenario, these values fall to 0.47 additional QALYs and £14,066 in additional cost savings.
Assuming an NHS and social services perspective, the probabilistic results indicate that the probability of early intensive ABA-based interventions being cost-effective at a threshold of £30,000 per QALY is <1% in the pessimistic scenario and 2.6% in the optimistic scenario. The probability that early intensive ABA-based interventions are cost-effective when assuming a public sector perspective is < 1% in the pessimistic scenario and 23% in the optimistic scenario. Taken at face value, these probabilities of cost-effectiveness indicate that there is relatively little chance that early intensive ABA-based therapy is cost-effective when pessimistic assumptions are made about the long-term effectiveness of early intensive ABA-based interventions, and a modest probability in the scenario when optimistic assumptions are made. Care should, however, be taken not to overinterpret these results, given the limitations of the economic model and the scope for further benefits or cost saving to alter this result.
The degree of decision uncertainty is illustrated in Figure 23, which presents the cost-effectiveness acceptability curve taking an NHS and social services perspective and a public sector perspective, respectively. The probability that early intensive ABA-based interventions are cost-effective when taking an NHS and social services perspective remains close to zero up to a threshold of £84,000 per QALY in the pessimistic scenario and up to £25,000 per QALY in the optimistic scenario. When a public sector perspective is adopted, the probability that early intensive ABA-based interventions are cost- effective begins to depart from zero at a threshold of around £30,000 per QALY under the pessimistic scenario and £1000 per QALY in the optimistic scenario.