Core Outcome Set and Unique Outcomes of Nursing Interventions for Women With Lactational Mastitis: A Mixed Methods Study

ABSTRACT Aims To develop the core outcome set and identify unique outcomes for the three stages and five types of nursing interventions, respectively, in lactational mastitis. Design A mixed methods study. Methods A systematic literature search, four semi‐structured interviews for key stakeholders, two rounds of Delphi surveys and two online consensus meetings were conducted. Results Thirty‐one nursing outcomes were derived from the systematic review (literature research from January 2019 to December 2021) and semi‐structured interviews in 2022. Six A‐category nursing outcomes and 19 B‐category nursing outcomes were determined after Dephi survey and provided in consensus meeting in 2023. The consensus meetings resulted in the agreement on seven core outcomes: Pain Level, Breast Establishment: infant, Breast Establishment: maternal, Breast Maintenance, Client satisfaction: care, Sleep, and Family Support during Treatment. Specifically, the unique outcomes for the three stages were identified as Breastfeeding Maintenance, Infection Severity and Wound Healing: Primary Intention, respectively. The unique outcomes for the five interventions included Pain level, Infection Severity, Wound Healing: Primary Intention, Comfort and Knowledge: breastfeeding, respectively. Conclusion Based on an evidence‐based, consensus‐driven approach, the core outcome set incorporates the perspectives of key stakeholders. It is recommended that all core outcomes be reported in both lactational mastitis nursing research and clinical quality control and audit. Unique outcomes should be reported based on the stages of lactational mastitis and types of interventions. Impact The core outcome set and unique outcomes developed by our study could provide nursing researchers and clinical practitioners with sensitive outcomes for lactational mastitis, while also promoting standardisation. Utilising these outcomes could enhance comparability among studies, reduce reporting bias and promote standardised evaluation of practice effectiveness. Reporting Method Findings are reported per Core Outcome Set‐STAndards for Reporting: COS‐STAR Statement. Patient or Public Contribution None. Trial Registration https://www.comet‐initiative.org/Studies/Details/1650