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

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Review of economic evaluations of ADHD drug interventions in children and adolescents
TABLE 66 Sensitivity analyses (excluding PEM)
Variable tested Cost-effectiveness with reference to non-treatment
comparator (Can $)
most cost-effective option for the management of
ADHD at Can$64 per CTRS point or Can$384 for
a six-point, one-SD gain, as shown in Table 65.
(For the PEM inclusive programme, high-dose
PEM was the next most cost-effective choice;
however, its effectiveness data were obtained from
one small study in 28 patients and no
consideration of hepatotoxicity was made.) DEX
did not show a six-point reduction in CTRS but
this estimate of lower efficacy was not statistically
significant. BT and combination therapies were
not shown to be effective in producing clinically
significant outcomes.
A number of one-way and extreme-case sensitivity
analyses were undertaken for both costs and
effects as shown in Table 66. A number of variables
were tested in the sensitivity analyses and MPH
remained the dominant strategy under most
assumptions. The results were not sensitive to the
upper CI of effectiveness data for DEX, BT and
combination therapy. Under the worst-case
scenario that favoured BT, the combination
therapy was no longer dominated; however, it was
still relatively less cost-effective (compared with no
treatment) than IR-MPH.
It is worth noting that the cost-effectiveness
estimates tested in the sensitivity analyses were
based on average cost-effectiveness (with the effect
being IR-MPH effect minus the no treatment
IR-MPH DEX BT Combination
Base case 83 D D D
Generic IR-MPH 75 D D D
School days only 119 D D 630
120% clinician fee 91 ED D D
80% clinician fee 76 D D D
Fewer counselling hours but same effect 83 D D D
Confidence limits 95 D D D
IR-MPH low 74 D D D
IR-MPH high 83 D D D
DEX low 83 D D D
DEX high 83 D D D
No treatment low 83 D D D
No treatment high 83 D D D
Combination low 83 D D D
Combination high 83 D D 311
Worst-case scenario (favouring BT) 103 D D 196
Weight 16 kg 66 ED D D
Weight 40 kg 101 D D D
D, dominated; ED, extended dominated, in weighted average with no-treatment comparator.
effect) per effect rather than incremental costeffectiveness.
There are a number of other caveats
that might be considered. Perhaps most
importantly one might question the key model
assumption that improvement in behavioural
rating scales is a good surrogate for clinically
significant improvements. It is not clear, from the
presentation of the results, whether the
distribution of change in CTRS is normal and,
unless this is so, estimating the number of patients
experiencing a six-point reduction using the
reported overall mean CTRS will not be accurate.
It has been shown that a change in the mean
CTRS score can give a different outcome
compared with calculating change in numbers of
respondents, if the distribution is non-normal
(Foster N, personal communication, 2004).
Therefore, it may be appropriate to estimate
response on an individual, patient-level basis.
The authors note that there is no proven decrease
in drug effectiveness over time and that any
change in length of drug therapy should result in
proportionate changes to both costs and effects
over time and therefore that the results may be
generalised to any time horizon. However, the
same may not be true of non-medical therapy
since, as Zupancic and colleagues 126 hypothesise,
BT effectiveness might change over time, arguing
that skills learnt in early counselling sessions
might be forgotten and therefore effectiveness