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

not fully probabilistic. The average daily drug
doses correspond to the moderate/high dose trials
in the clinical effectiveness review in Chapter 4.
Utility data
The review of the literature in Chapter 5 illustrated
that there are few sources of data on utility for
children and adolescents with ADHD. Two of the
manufacturers’ submissions used utility values
obtained using an SG technique from parents of
children with ADHD, providing proxy valuations
for their children. These utility estimates were
available in the public domain as poster
presentations. The first set of utility values 136,155
provided an estimate of the utility of a responder
to treatment (mean 0.837, standard error 0.039)
and a non-responder to treatment for ADHD
(mean 0.773, standard error 0.039), independent
of the treatment being received. These values are
used in the base case analysis. The second set of
available utility values 145,156 provided estimates of
the utility of responders and non-responders, with
and without side-effects, that were treatmentspecific.
There were some concerns over the
validity of these estimates, as detailed in Chapter 5,
so these are employed in a sensitivity analysis.
None of the available utility values were obtained
with the use of a generic health valuation measure
valued with public preferences, as recommended in
guidance from NICE. 157 This is a common
problem when assessing QoL in children.
The uncertainty around these estimated utility
values was characterised using a beta distribution,
as it was felt reasonable to assume that the values
would not drop below zero.
Results
Response and withdrawal rates in the
base case analysis
In the base case analysis, the definition of
response was defined as a score of 1 or 2 on the
CGI-I. This restricted the number of included
Health Technology Assessment 2006; Vol. 10: No. 23
TABLE 89 Average dose and unit cost used in economic model: IR-MPH, ER-MPH8, ER-MPH12, ATX and DEX
Treatment Average dose per day Average dose per day Cost per day titration Cost per day after
during titration (mg) following titration (mg) period (£) titration period (£)
IR-MPH 22 39 0.36 0.64
ER-MPH8 25 41 1.27 1.58
ER-MPH12 27 35 1.33 1.76
ATX 28 45 2.15 2.19
DEX 14 22 0.19 0.42
© Queen’s Printer and Controller of HMSO 2006. All rights reserved.
trials to six of the 65 identified in the clinical
effectiveness review in Chapter 4. The estimated
response rates were subject to large uncertainty,
which is unsurprising given the small size of some
of the included studies, the restricted amount of
data available and the heterogeneity between
trials. The output of the WinBUGS model is
shown in Table 90.
The estimated response rates are all in the
expected direction given the trial evidence.
However, it must be noted that the volume of trial
data is small and varies between treatments. Data
on the effectiveness of IR-MPH were available in
four trials (154 patients), ER-MPH8 in one trial
(154 patients), ER-MPH12 in two trials (920
patients), ATX in one trial (473 patients) and DEX
in one trial (32 patients). The uncertainty in the
calculated response rates incorporates the size of
the evidence base for each treatment.
Cost-effectiveness results for the base
case analysis
The base case analysis assessed the costeffectiveness
of alternative treatment strategies,
comprising drug monotherapies followed by no
treatment. Nineteen relevant strategies were
compared, including a no treatment option (see
Table 85), over a time horizon of 1 year. The
results from this analysis identified a dominant
treatment strategy, number 13, which was
associated with the lowest costs and the highest
QALY gains relative to other comparators.
However, the difference in QALY gains between
the active treatment strategies was very small. This
is unsurprising given the uncertainty surrounding
the relative clinical effectiveness of the active
treatments. Also, the loss of QoL by trying an
ineffective treatment before a relatively more
effective one will endure for only 1 month before
non-responders move to the next treatment in
sequence. Table 91 shows the results from the base
case economic analysis, employing the response
and withdrawal rates shown in Table 90. The
results should therefore be interpreted with
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