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Wanted: better approaches to deal with complexity in health systems research

The last few years, complexity has emerged as a key issue in health systems research. It is now generally acknowledged that health interventions often take place in settings or health care systems that are complex and that this requires adapted research and evaluation methods.

At the same time, dissatisfaction with ‘traditional’ quasi-experimental designs has emerged, because they focus on testing effectiveness but overlook the underlying processes of change and the context conditions that are needed for success.

In collaboration with:

Logo KITDepartment of Development, Policy and Practice
Royal Tropical Institute, Amsterdam


Weaknesses of commonly used research methods

Most current research and evaluation methods in health systems research do not sufficiently take into account complexity.

  • Quasi-experimental methods focus on outcomes and impact
  • They do not take enough into account the influence of the context in which the intervention took place
  • They rarely expose the mechanisms that make the intervention work
  • Case studies, action research and process evaluations provide context-specific information, but their findings are difficult to generalise

Such studies are not very useful for policymakers. Research should indicate whether interventions work (or not), but they ideally also provide information on the conditions that are required and the mechanisms that underlie success. This is what policymakers and planners need in order to design the appropriate intervention for their context.

The chapter on theory-driven inquiry seeks to provide this information.

Theory-driven inquiry

The domain of theory-based evaluation has seen quite some evolution since the 1970s. Under the label Theory-driven inquiry, we present three main evaluation approaches that share a strong focus on the theory on which an intervention is based. They all aim at explaining how an intervention works and in which conditions.

Theory-driven evaluation

Theory-driven evaluation emerged in the discipline of evaluation in the 1980s. Chen and Rossi developed it as an answer to policy and programme evaluation approaches that remained limited to before-after and input-output designs, or that focused narrowly on methodological issues.

Realist evaluation and synthesis

Realist evaluation intends to answer the question: “Why does this intervention work, for whom and in what circumstances?”

In other words: which mechanism(s) cause which outcome(s) in which conditions? Realist inquiry has an explanatory focus and aims to unravel mechanisms of change. It is applied in research and evaluation, and in synthesis of evidence.

Theories of change

The Theory of Change approach (ToC) was developed by the Roundtable on Community Change (Aspen Institute, USA).

Pragmatic in its approach, ToC is used to evaluate community-based programmes that typically involve many agencies and actors, have several levels and strands of activities, objectives and strategies that shift in time, and outcomes that are difficult to measure (Read more).

Nothing as practical as a good theory
(Weiss 1995)


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    TDI workshop

    On 22 and 23 November 2010, the Unit of Health Care Management, Department of Public Health (ITM), organised an international expert meeting on theory-driven evaluation.

    About 15 researchers presented research and evaluations and discussed the methodological challenges of realist evaluation, theory-driven evaluation and realist synthesis in health systems research.

    In total 30 researchers, policymakers and programme managers attended the workshop.

    About this website

    This theory-driven inquiry website is developed by the Health Care Management Unit of the Department of Public Health, Institute of Tropical Medicine, Antwerp and the Development Policy & Practice Unit of the Royal Tropical Institute, Amsterdam. We collaborate on the development and implementation of theory-driven inquiry in health systems research, and aim at stimulating a better understanding of the advantages of this approach among both researchers and policymakers. To this end, we are engaged in a number of research and evaluation studies that use TD inquiry principles.

    Institute of Tropical Medicine

    Unit of Health Care Management

    TD inquiry project evaluations
    Défi Jeunes

    TD inquiry research projects
    PhD Bruno Marchal
    PhD Pierre Blaise

    The cluster Research methodology for complexity in healthcare


    Bruno Marchal - personal page
    Guy Kegels - personal page
    Tom Hoerée
    Josefien Van Olmen - personal page
    Sara Van Belle




    Royal Tropical Institute

    Department of Development, Policy and Practice

    TD inquiry project evaluations

    Realist evaluation of ASHA program in a district (India)

    TD inquiry research projects

    Realist inquiry in capacity building
    PhD Marjolein Dieleman

    Research and evaluation methodology

    Marjolein Dieleman
    Barend Gerretsen
    Sumit Kane
    Prisca Zwanikken