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

previous treatment. These caveats must be borne
in mind when interpreting the model results.
Limitations of the clinical
effectiveness studies and need for
further research
The limitations of the research base remain similar
to those reported in the previous NICE review and
in other SRs.
● Generally, the methodology used in the studies
was poorly reported. Inadequate information
makes it difficult to assess validity and reliability
of the studies.
● The literature is dominated by studies of MPH,
although the quality of these studies is generally
poor. For DEX, both the quantity and quality of
studies are poor. For ATX, there are few studies,
but most are of better quality. The quantity and
quality of studies evaluating MPH, DEX and
ATX should be a consideration for future
research. Researchers should use the
CONSORT approach to study design. 159
● Very few studies compared MPH and DEX
directly. No studies compared ATX and DEX
directly. More head-to-head studies may be
beneficial.
● Most of the studies report short-term outcomes.
More long-term studies are needed to establish
clinical effectiveness and adverse events.
● There is an almost total absence of research
investigating the effectiveness of MPH and
other interventions for children with a diagnosis
of hyperactivity disorder, rather than the
broader diagnosis of ADHD. This may have
implications for the generalisability of these
studies in the UK where HKD makes up most of
the cases.
● The majority of studies have been conducted on
children between the ages of 5 and 13 years.
More studies in adolescents may be useful.
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Health Technology Assessment 2006; Vol. 10: No. 23
● It appears that, in some cases, parents are less
likely than teachers to rate children as being
improved.
● It may be useful when possible to collect data
from the children to obtain a better
understanding of treatment from a patient’s
perspective and to estimate patient-based
measures of clinical outcome.
● The studies used a number of outcomes and
scales to measure behaviour, including
hyperactivity, making comparisons of results
difficult. It would be beneficial if research
groups selected a core set of validated and
clinically relevant outcomes to be measured in
all studies, and to be consistent in analysing and
reporting the results.
● A number of studies used a crossover design;
however, the data were not always analysed
using a method specific to paired data.
Presenting within-patient differences (and
associated SDs) would be useful.
● A number of the included studies have small
sample sizes. Presenting sample size calculations
would be useful in order to make sure the
studies are not underpowered, so that clinically
significant differences between interventions are
detected. As part of sample size calculations,
authors should clearly specify a clinically
significant effect on a particular outcome
measure.
● Very few studies included in the review
presented usable data for analysing adverse
events. Standardised reporting of data (e.g.
presenting the numbers of adverse events,
numbers of participants suffering from adverse
events and total numbers of participants
included in the safety analysis) is required to
estimate prevalence.
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