Conceptualising Health Systems for Economic Evaluation:A Review and Framework for Health System Models

Multi-disease Health System Models (HSMs) represent a new frontier in economic evaluation, enabling decision analysis for sector-wide resource allocation in the context of interacting health needs, system capacity and financial constraints. To support the development of conceptually grounded HSMs, we conducted a meta-narrative review of conceptual frameworks from the economic evaluation and health system assessment literature to understand how health systems and their relationships with different types of outcomes have previously been represented. Four main approaches were identified: health systems as a set of functions, as production constraints on overall healthcare, as intervention-specific constraints along the care pathway, and as complex adaptive systems. We assess the strengths and limitations of each in informing the structure, scope, and causal logic of HSMs. Drawing from our experience developing the Thanzi La Onse model of Malawi’s health system, we propose a new conceptual framework for HSMs, grounded in theory of change principles and informed by prior literature on health system assessment. The framework is designed to support the full lifecycle of HSMs, from model design and intervention representation to the transparent communication of assumptions and results. By clarifying causal pathways, enabling the representation of diverse interventions, and facilitating stakeholder engagement and policy translation, the framework provides a bridge between high-level conceptual thinking and the operational needs of policy-relevant modelling. This work seeks to advance how health sector policies and investments are conceptualised in economic evaluation and to guide the continued development of health system modelling approaches.