Improving the evidence base for practice: a realistic method for appraising evaluations

Introduction: To present and discuss a method for the appraisal of evaluations which can be used by the informed practitioner and will facilitate the incorporation of research evidence into every day nursing, midwifery, and health visiting practice. Background: The development of current systems for the appraisal of published studies is described, showing that they still reflect their origin in experimental methodology, despite increasing awareness of the potential contribution of non-experimental work to the evidence base for healthcare practice. The difficulties that this creates for practitioners are then explored. Appraising evaluations: The unique character of evaluation studies is emphasised. We contend that the underlying unity of purpose is more important than methodological distinctions. Four key questions to shape the appraisal of such studies are presented. Drawing on the methodological work of Campbell and Stanley (1966) we propose a method for answering these questions which focuses on the assessment of threats to internal validity. The system in use: Finally, a worked example of the system in operation is provided. We discuss the issues which this raises, and conclude that the system permits a more practical and accessible method for appraising the evidence produced by evaluation studies