Exploring definitions of porcine respiratory disease complex in the literature: a scoping review protocol.

Background: Porcine respiratory disease complex (PRDC) is a major health and economic concern in commercial swine production, contributing to reduced growth performance, increased mortality, elevated treatment costs, and widespread antimicrobial use. Although the term and its acronym are widely used in both research and clinical practice, its definition varies considerably across studies. Definitions may rely solely on clinical signs or incorporate combinations of pathological findings, laboratory diagnostics, performance indicators, and environmental or management factors. This lack of definition consistency challenges disease surveillance, diagnosis, and comparability across studies, potentially hindering the development of effective interventions. Scoping reviews are particularly suited for clarifying how complex terms are defined, mapping research approaches, and identifying gaps in knowledge. The objective of this scoping review is to systematically map and describe how PRDC has been defined and operationalized in the scientific literature. Methods and analysis: This review will follow a five-step refined methodological framework guided by the Joanna Briggs Institute. Eligible sources will include peer-reviewed and grey literature published in English language from 1990 onwards. Searches will be conducted in PubMed/MEDLINE, Web of Science, CAB Abstracts, and Scopus, supplemented by grey literature sources such as OpenGrey, ProQuest, and Google Scholar. Additionally, all open-access issues of the Journal of Swine Health and Production will be manually reviewed. Two reviewers will independently screen titles, abstracts, and full texts, with disagreements resolved by consensus or a third reviewer. Data will be extracted on study characteristics, PRDC definitions, diagnostic criteria, pathogens considered, and production context, including environmental and/or housing/management conditions. Results will be reported in accordance with PRISMA-ScR, using descriptive tables and narrative synthesis to explore variability and consistency in PRDC definitions. Discussion: This protocol outlines a scoping review designed to chart how PRDC has been defined in swine health research. By identifying areas of consensus and divergence, the review will support the development of more consistent case definitions, enhance cross-study comparability, and inform future research and systematic reviews.