Workstream 3

Study 7: Economic model development

A decision-analytic model will be developed, informed by the concept map in Study 1. Compared with trial-based economic evaluations, economic models have an advantage in that they can consider a wider range of information beyond just the trial (e.g. outcome extrapolation). To address limitations of many health economic models, our approach to model building will be modular (self-contained components can be linked together) and iterative (the model updates and extends as new data becomes available). The model building will start with a simple comparative decision-analytic model based on population aggregates and will then increase in complexity based on the concept map and data availability. Add-ons will include the spatial epidemiology model developed in Study 2, choice models developed in Study 5, and a synthetic microdata population derived from datasets analysed in Study 2. These additions will facilitate analyses capturing geographic variation, which explore heterogeneity, equity, and choice behaviour. The model will account for uncertainty around input parameters and examine the robustness of results. Health outcomes will include prevalence and sequelae of key chronic diseases (including but not limited to depression, anxiety, diabetes and cardiovascular disease). Quality Adjusted Life Years (QALY) will be modelled as they are an important outcome for economic evaluation and are recommended by the Pharmaceutical Benefits Advisory Committee in Australia. Model validation will include face-validity review by the Steering Committee and Community Advisory Group, cross validation with other published models and comparison of model predictions with observed data from the sources explored in Workstream 1. An open-source model will be developed and used in Study 8 to assess the cost-effectiveness of selected interventions. This will also serve as a decision aid for use by service planners to help decide future investments.

Study 8: Modelling the cost-effectiveness and equity impacts of selected interventions

The interventions identified in Study 7 will be evaluated for cost effectiveness and equity (across geographical regions, illness categories and population sub-groups). The Steering Committee and Community Advisory Group will review results and help provide solutions to important implementation considerations. The primary analytic model chosen will be cost-utility analysis (CUA) with outcomes expressed in terms of 'cost per QALY gained' for the intervention population compared to current practice. The secondary economic framework will be a return on investment framework, focusing on costs and cost-offsets. The intervention pathway and effectiveness will be sourced from the literature via systematic reviews. The cost effectiveness analysis will adopt both a healthcare perspective and a societal perspective, including productivity or informal care impacts. Results from CUA will be assessed against commonly used cost-effectiveness thresholds. Univariate and multivariate sensitivity analyses will be conducted to assess the robustness of the results when adopting different assumptions. Cost-effectiveness findings will be presented alongside key implementation considerations (strength of evidence, equity, acceptability, feasibility, and sustainability), which will be derived from consultations with the Steering Committee. We will develop recommendations of a ‘menu’ of cost-effective interventions to inform policy-decisions that can be updated as more evidence is produced.