Combining causal inference and within-trial economic evaluation methods to assess comparative cost-effectiveness using real-world data: a tutorial with recommendations based on the quasi-experimental ADAPT study of a redesigned mental health service.


The ‘Assessing a Distinct IAPT service’ (ADAPT) study used NHS Talking Therapies (TTad), previously called Improving Access to Psychological Therapies (IAPT), routine data to evaluate an Enhanced TTad service compared to treatment-as-usual. We combined economic evaluation and causal inference methods to produce economic evidence while controlling for confounding and selection bias in our estimates.

Our primary analyses suggested the Enhanced service had a high probability of being cost-effective (e.g., >95%), driven by the potential to be cost-saving rather than providing additional health gains based on quality-adjusted life years (QALYs). The whole evaluation was based on only TTad services routine data, which was pragmatic and cost-efficient, but had limitations such as the potential for unobserved confounding and not accounting for impacts on the wider NHS. Despite this, the results are useful for TTad services commissioners and provided useful learning for future studies. Preprint available here; statistical analyses publication available here.

Our next study will:

  • We are planning on conducting further evaluations using TTad services routine data linked to other sources including hospital and prescribing data, to compare different talking therapies head-to-head and to explore potential inequalities in outcomes,
  • We are exploring how TTad service data linked to other healthcare data could inform clinical guidance and evaluation processes, such as developed or conducted by the National Institute for Health and Care Excellence (NICE) within England and Wales
  • Further studies could aid TTad service reform and refinement, but also suggest to what extent current routine data collection is sufficient for generating real-world evidence on comparative effects, or if further or different data collection or linkage is required.


Currently Underway

Team Contact:

Senior Health Economist Research Fellow

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