The main conclusion from all the meta-analyses is that receiving early high-intensity ABA-based intervention leads to somewhat greater improvements in IQ and VABS scores than if receiving low-intensity, TAU or eclectic interventions. IQ scores were higher by at least 9 points (about 0.6 of a SD) from 1 year after initiation of intervention onwards (MD 9.16, 95% CI 4.38 to 13.93). Scores on the VABS components were higher in the ABA intervention arms by 6–8 points on average (0.8 of a SD) after 2 years (composite score: MD 7.00, 95% CI 1.95 to 12.06). Improvements at 1 year appeared to be smaller and were not generally statistically significant.
Heterogeneity, estimated by I2, was generally low, but this was a consequence of the small size of most
included studies, which makes it difficult to conclusively identify heterogeneity. There was, however, considerable variation in effect estimates across studies for some outcome measures. For example, MDs in composite VABS at 2 years ranged from –4.79 to > 33. There was also variation across studies in how the outcome measures changed over time. This raises some concerns of whether or not studies are comparable.
There were few data on the longer-term impact of early intensive ABA-based interventions beyond the end of the main intervention period. Only one study reported results at 7 years after initiation, which found no difference between early intensive ABA-based and comparator arms. It is therefore not possible to determine the long-term impact of early intensive ABA-based interventions, including whether or not any benefits observed at 2 years persist.
Other outcomes
Results for other outcomes were limited due to the small numbers of studies reporting them. Data on autism symptom severity were too limited to be conclusive, with no clear evidence that early intensive ABA-based interventions improved the severity of autism compared with TAU or eclectic interventions. There were, similarly, limited data on language comprehension. Three studies85,89,104that used the RDLS
scale found some evidence that language scores favoured the early intensive ABA-based group compared with TAU or eclectic interventions by around 11 points (RDLS comprehension at 2 years: MD 11.78, 95% CI 2.12 to 21.44). By contrast, two studies93,97that reported the MSEL expressive and receptive
language subscales found no difference in scores between the two groups. There were insufficient data on behaviours that challenge to permit any meta-analysis. The limited data from one study90suggested
that early intensive ABA-based interventions could reduce behaviours that challenge, but results were not statistically significant.
School placement was available in only one study89comparing early intensive ABA-based interventions
with TAU and eclectic interventions, and in two studies26,103comparing high- with low-intensity ABA-based
interventions. These studies suggested that children receiving a high-intensity ABA-based intervention were much more likely to be in mainstream education (possibly with support) than children receiving TAU, eclectic or low-intensity ABA-based interventions. This analysis, however, may be confounded by parental preference for early intensive ABA-based treatment and mainstream schooling placement, and the practice in Lovaas26of encouraging children to change school if teachers became aware of their autism.26
Consequently, there is no good-quality evidence to suggest that early intensive ABA-based interventions independently influences school placement.
Participant and study characteristics
Studies reported limited data on child and parent characteristics, or details of how early intensive ABA-based interventions were administered. It was therefore not possible to investigate most of the protocol-specified covariates and how they might influence the effectiveness of early intensive ABA-based interventions. We found no conclusive evidence that age, sex, baseline IQ or baseline VABS score had any impact on the effectiveness of early intensive ABA-based interventions when compared with other interventions.
There was no generally clear evidence that study-level covariates, including delivery setting, allocation, parental involvement, duration and intensity of early intensive ABA-based treatment, had any clear or observable impact on the MDs between these interventions and comparator groups. A possible exception was that trials from earlier years found larger impacts on VABS composite score than later trials, although the power to detect such differences was limited as there were few studies in the analysis.
Comparison of applied behaviour analysis-based interventions
Sensitivity analyses and the NMA both found no evidence of any difference in effectiveness between TAU and eclectic interventions or any difference in effectiveness between different types of ABA-based early intervention (EIBI alone or with NDBI). There was no evidence that parent-managed interventions differed in effectiveness from other forms of management.
There was some evidence that high-intensity EIBI may be more effective than low-intensity EIBI, and that high-intensity ABA-based intervention, in general, may be more effective than low-intensity interventions (whether low-intensity ABA based or eclectic interventions). This may suggest that it is the high intensity of the intervention that causes the greater benefits, rather than the precise nature of the intervention received.
RESULTS OF INDIVIDUAL PARTICIPANT DATA META-ANALYSIS
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Chapter 7
Economic analysis
Overview
This section outlines the development of a new economic model assessing the cost-effectiveness of implementing early intensive ABA-based interventions in a UK context.
The cost-effectiveness model built on the IPD meta-analysis presented in Chapter 6, using its results to inform the model parameters for the effectiveness of early intensive ABA-based interventions. Most of the available evidence focused on cognitive ability (IQ) and adaptive behaviour (VABS), with few data on other outcomes. In developing the model, we therefore sought to link these two outcomes to both cost and benefits.
This narrow focus on these two outcomes has important implications for the interpretation of the economic model. It means that the model does not account for effects on other outcomes and may not fully capture the benefits of early intensive ABA-based interventions. The economic model is therefore only valid to the extent that the benefits of early intensive ABA-based interventions can be captured by changes in cognitive ability and adaptive behaviour scores.
The IPD meta-analysis also identified a number of important limitations in the effectiveness data. In particular, the review raised concerns about the reliability of treatment effect estimates, given the weakness in the methods used in the primary studies. The interventions and comparators assessed also varied and it not clear how well they reflect how early intensive ABA-based interventions or other interventions are used in the UK.
In consequence of these limitations, the presented economic model should not be viewed as a
comprehensive assessment of the cost-effectiveness of early ABA-based therapy, as the data currently available are insufficient to make inferential judgements. Instead, it is more appropriate to view the model as an exploratory analysis that provides a vehicle with which to explore key drivers of cost-effectiveness, while also providing indicative results of any potential cost-effectiveness of early intensive ABA-based interventions.