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Republished: How to study improvement interventions: a brief overview of possible study types
  1. Margareth Crisóstomo Portela1,2,
  2. Peter J Pronovost3,
  3. Thomas Woodcock4,
  4. Pam Carter1,
  5. Mary Dixon-Woods1
  1. 1Social Science Applied to Healthcare Research (SAPPHIRE) Group, Department of Health Sciences, School of Medicine, University of Leicester, Leicester, UK
  2. 2Department of Health Administration and Planning, National School of Public Health, Oswaldo Cruz Foundation, Rio de Janeiro, RJ, Brazil
  3. 3Departments of Anesthesiology, Critical Care Medicine, and Surgery, Armstrong Institute for Patient Safety and Quality, School of Medicine, and Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland, USA
  4. 4NIHR CLAHRC for Northwest London, Imperial College London, Chelsea and Westminster Hospital, London, UK
  1. Correspondence to Dr Margareth C Portela, Departamento de Administração e Planejamento em Saúde, Escola Nacional de Saúde Pública, Fundação Oswaldo Cruz, Rua Leopoldo Bulhões 1480, sala 724—Manguinhos, Rio de Janeiro, RJ 21041-210, Brazil; mportela{at}


Improvement (defined broadly as purposive efforts to secure positive change) has become an increasingly important activity and field of inquiry within healthcare. This article offers an overview of possible methods for the study of improvement interventions. The choice of available designs is wide, but debates continue about how far improvement efforts can be simultaneously practical (aimed at producing change) and scientific (aimed at producing new knowledge), and whether the distinction between the practical and the scientific is a real and useful one. Quality improvement projects tend to be applied and, in some senses, self-evaluating. They are not necessarily directed at generating new knowledge, but reports of such projects if well conducted and cautious in their inferences may be of considerable value. They can be distinguished heuristically from research studies, which are motivated by and set out explicitly to test a hypothesis, or otherwise generate new knowledge, and from formal evaluations of improvement projects. We discuss variants of trial designs, quasi-experimental designs, systematic reviews, programme evaluations, process evaluations, qualitative studies, and economic evaluations. We note that designs that are better suited to the evaluation of clearly defined and static interventions may be adopted without giving sufficient attention to the challenges associated with the dynamic nature of improvement interventions and their interactions with contextual factors. Reconciling pragmatism and research rigour is highly desirable in the study of improvement. Trade-offs need to be made wisely, taking into account the objectives involved and inferences to be made.

  • Statistical process control
  • Social sciences
  • Quality improvement methodologies
  • Health services research
  • Evaluation methodology

This is an Open Access article distributed in accordance with the terms of the Creative Commons Attribution (CC BY 4.0) license, which permits others to distribute, remix, adapt and build upon this work, for commercial use, provided the original work is properly cited. See:

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