A systematic review and economic model of the effectiveness and ...

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Economic model
Probabliity cost-effective
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0 10,000 20,000 30,000 40,000 50,000 60,000
Willingness to pay per QALY (£)
FIGURE 26 Cost-effectiveness acceptability frontier showing the optimal strategies in a sensitivity analysis of long-term extrapolation
expected net benefit. The cost-effectiveness
frontier for this sensitivity analysis is shown in
Figure 26. Strategy 7 appears cost-effective for
values of willingness to pay per QALY above
£7128, and strategy 9 does not appear to be costeffective.
Clearly, this model does not incorporate long-term
adverse effects of pharmacotherapy, as the data
were not available to include this, and this is an
important omission from the model. The model
also does not include long-term benefits of
treatment, which could perhaps be avoidance of
prison, lower numbers of exclusions from school
and improved peer relations. However, this
omission is less critical, because the inclusion of
these benefits would only improve the costeffectiveness
of active treatment.
Sensitivity to estimated resource use
In the base case model, the no treatment option
(strategy 19) is dominated by an active treatment
option. This is due in part to the estimates of
resource use employed in that model, in particular
the fact that a non-responder is more costly in
terms of non-drug resource use compared with a
responder. In the submission by Celltech, an
alternative assumption was used regarding
resource use. They followed the Wessex DEC
evaluation 124 in assuming that responders to
13
7
treatment had six visits to a psychiatrist per year
and six visits to a GP per year. Non-responders
were assumed to have only two visits to a GP per
year, and were therefore less costly than
responders in terms of non-drug resource use.
In this sensitivity analysis, we evaluate the impact
on the model results of employing this alternative
source of resource use. The uncertainty
surrounding the resource use was characterised
using a gamma distribution. The 95% CI for the
numbers of psychiatrist and GP visits for
responders was assumed to be 3 to 9 per year. The
95% CI around the number of GP visits for nonresponders
was assumed to be 0 to 4 per year. The
results of this analysis are shown in Table 96.
Strategy 19 (no treatment) is no longer
dominated.
The cost per QALY gained with strategy 13 (firstline
DEX, second-line IR-MPH, third-line ATX)
compared with strategy 19 is £14,939. Strategy 13
remains the optimal treatment strategy in this
sensitivity analysis with radically different
estimates of resource use.
If DEX is not suitable as first-line therapy, strategy
7 (first-line IR-MPH, second-line DEX, third-line
ATX) remains the optimal treatment strategy, with
a cost per QALY gained of £15,662 compared with