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

The probabilistic results were used to construct
cost-effectiveness acceptability curves (CEACs)
comparing all five treatment strategies, according
to the method described by Fenwick and
colleagues. 137
[Confidential information removed].
Comments on methodology
Time horizon
Although ADHD is a chronic condition, the
submission assesses the cost-effectiveness of the
alternative treatment strategies over the course
of 1 year. [Confidential information removed].
It is important to note that although the
treatment decision may be reviewed annually, the
decision problem at the point of review is different
to the initial treatment decision. At the point of
review, the GP will know which treatments the
patient has failed to respond to, which caused
adverse events and which produced a favourable
response.
[Confidential information removed].
The consequence of the short time horizon is that
long-term implications of treatment for ADHD are
not considered. As a consequence, it is difficult to
know how cost-effective Concerta XL would
appear over a time horizon longer than 1 year.
Use of trial data
The cost–utility model in the submission made
very selective use of the body of evidence
concerning the efficacy of the alternative
treatment strategies. The effectiveness evidence
was based on only three trials, 90,99,133 out of 65
potentially relevant studies identified in the
clinical effectiveness review in Chapter 4. The
justification for ignoring the majority of the RCT
data was that double-blind, double-dummy trials
cannot assess the effectiveness of a once-daily
extended release formulation of IR-MPH in
comparison with twice- or three times daily
administration of IR-MPH as both arms receive
the same number of pills. Janssen-Cilag argue that
compliance to a product given once in the
morning may be higher than one needing to be
taken during the school day, and hence they make
use of two open-label pragmatic randomised
trials. 90,99
[Confidential information removed].
The response rates to BT, [Confidential
information removed] were taken directly from
the MTA trial. 133 This extraction of data from
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Health Technology Assessment 2006; Vol. 10: No. 23
single arms of a trial breaks the randomisation,
and implicitly assumes that the baseline
characteristics of the patients in the CON-CAN-1,
FOCUS and MTA trials are identical. This is
unlikely to be the case and this methodology is
inappropriate. A more appropriate approach
would have been to take the relative treatment
effects from each study and apply them to a
common baseline. Finally, the definition of
response for ATX [Confidential information
removed] differs from that used for the other
comparators considered in the model (£1 mean
parent-rated SNAP-IV score). This is most likely
due to a lack of outcome data employing the
SNAP-IV scale for ATX. The submission does not
provide evidence as to the comparability of these
two definitions of response.
The discontinuation rates were also based only on
CON-CAN-1 [Confidential information removed].
This limited use of data will fail to incorporate
differences in side-effect profiles between these
drugs. The costs associated with adverse events
were also not differentiated by drug. In this respect,
it is important to consider that the minimum dose
of Concerta XL is 18 mg per day, as it is not
possible to divide the extended-release capsules.
This compares with a minimum dose of 5 mg with
the other drugs, and so patients requiring 18 mg and