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

only level of social disability that IHRQoL
includes is slight social disability. This is an oftcited
criticism of generic indexes of HRQoL: that
their content validity may be weak when applied
in specific disease areas. In practice, the IHRQoL
is rarely used today and values of health states
were gained from a small sample of individuals
whose preferences are unlikely to be representative
of the population of England and Wales as a
whole. The authors undertook multi-way
sensitivity analyses in order to explore the effect
that modelling plausible variations in quality of
life improvements pre- and post-treatment had on
cost–utility estimates. Overall, the effect of
modelling different disability/distress levels had
little impact on the estimates. The authors did not
report on any uncertainty associated with the
QALY estimates.
An alternative approach to employing a generic
preference-based health index of HRQoL is to
describe health states specific to the disease under
consideration, and value them directly using
techniques such as SG or TTO. The validity of
these measures depends on the content and style
of the vignette used to describe each health state.
Matza and colleagues 125 published an abstract
including utility information based on the SG
technique. Utility information was elicited from 43
parents of children with ADHD. Eleven
hypothetical health states were developed based
on the opinion of doctors and informed by
published literature and unpublished clinical trial
data. Health states that were valued included
untreated ADHD, stimulant treatment and nonstimulant
treatment (e.g. ATX). The actual
vignettes used to describe each health state were
not available to us as the study is currently
published only as an abstract. The parents rated
each health state including the current health state
of their child (mean parent SG rating = 0.74), and
the SG utility scores varied from severe untreated
ADHD (0.48) to effective, tolerable ATX nonstimulant
treatment (0.88). However, the full
range of utilities for all 11 health states was not
reported in the abstract and neither were any data
on the variation around each estimate. The
authors stated that comparisons between health
states found expected differences between
untreated mild, moderate and severe ADHD
states. In the case where stimulant and nonstimulant
medication were both effective and
tolerable, parents preferred the latter (ATX)
(p < 0.03).
A potential advantage of this approach, therefore,
is that small differences in health states can be
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Health Technology Assessment 2006; Vol. 10: No. 23
estimated in terms of utility values. Also, with
reference to this review, the values are based on
direct patient valuations, rather than expert
judgement. We note that NICE prefers a generic
and validated classification system for the
estimation of health state utilities. However, the
estimated utilities available for ADHD using
generic instruments are crude, and based on
expert opinion. Hence values obtained directly
from patients, using SG methodology, may be
more relevant for this review.
Cost-effectiveness
Five relevant economic evaluations were found in
the published literature, 4,123,126,128,129 including
Lord and Paisley, 4 which was part of the original
NICE appraisal. (Reference 126 is reported in the
economic evaluation section of Miller and
colleagues 30 and is also reported in brief in Shukla
and Otten 127 .) The last two studies 128,129 are not
formal economic evaluations since costs were not
compared with outcomes for the interventions
being assessed. However, they do include the
benefit of response to treatment in terms of
reduced costs and therefore provide useful data.
Gilmore and Milne 123 assessed the cost-utility of
IR-MPH compared with placebo for children
diagnosed using DSM Criteria for Pervasive
ADHD/ADDH 2 or Barkley’s research criteria 130
who are otherwise normal. Gilmore and Milne 123
argue that they chose to use placebo-controlled
trials as placebo effects are important.
The NHS healthcare perspective was adopted and
utility information was determined as described in
the QoL section above. In terms of resource use,
the dosage of MPH and the average number of
outpatient clinic attendances over the year were
estimated based on the opinion of five child and
adolescent psychiatrists (personal communication:
it is likely that paediatricians’ case loads have
different population characteristics and that this
will have significant implications for the number
of attendances. It should be acknowledged that
the growing development of nurse-led ADHD
services will also have economic implications). It
was assumed that all follow-up was hospital-based,
that those who terminated treatment or those who
did not respond were treated for 6 weeks, on
average, and that those who were included in the
analysis for 1 year received five outpatient
appointments. Additional information on drug
dosages was obtained from the literature, and data
on children’s weights were taken from percentile
charts. The cost of the drugs was obtained from
MIMS (August 1997) 131 and the cost of child and
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