Background: Adults with cystic fibrosis (CF) experience, on average, two to three pulmonary exacerbations per year. Exacerbations are associated with a decline in lung function and increased mortality, result in high symptom and treatment burden and present self-management challenges for patients. Little is known about the emotional impact of exacerbations and how it relates to self-management. There are no patient-reported outcomes measures (PROMs) currently available to assess symptom distress and self-management during a pulmonary exacerbation in CF, limiting the ability to evaluate interventions in support of exacerbation-related self-management. Aim and objectives: The aim was to develop and conduct preliminary validity testing of a PROM for measuring a concept of relevance for symptom management during pulmonary exacerbation in adult CF patients, guided by the Food and Drug Administration (FDA) framework. Objectives were to: i) critically review PROMs related to symptom management in CF and appraise their suitability of use during exacerbations (Phase 1); ii) identify and describe current gaps in knowledge regarding CF patients experience of a pulmonary exacerbation (Phase 2); iii) explore patientsâ€™ experience (Phase 3); iv) develop a conceptual framework for symptom management in exacerbations (Phase 4); and v) develop a draft item list and assess content validity and clarity (Phase 5). Methods: A multistage study was undertaken, comprising qualitative methods (Phase 2), and two convergent mixed-method studies (Phases 3 and 5) Results: Phase 1: Five PROMs were included in the review; none measured the concept of symptom distress or self-management during exacerbation. Phase 2: The thematic synthesis of qualitative studies identified a broad spectrum of physical and emotional symptoms experienced by patients but data relating to experiences during exacerbation were limited. Phase 3: The mixed-method study (n=18) revealed that pulmonary exacerbations are characterized by an increase in emotional distress, which was linked to the meaning associated with the exacerbation. Experiencing a pulmonary exacerbation meant being â€˜thrust out of normalityâ€™ and indicated a period of threat and life domination by CF. Symptom and treatment burden consumed energy and placed restrictions on physical activity and daily life roles. Phase 4: Based on a review of relevant theoretical frameworks, a conceptual model describing illness-related emotional distress was developed. Phase 5: A list of 27 items were extracted from patient interviews (Phase 3) which were underpinned by the conceptual framework (Phase 3 & 4). Clinical experts (n=12) and patients (n=8) rated the concept â€˜emotional distressâ€™ as relevant and comprehensively covered by the item list, and agreed that the draft PROM layout and wording were easily understood. Following this consultation, three further items were added (giving a total of 30 items) and yielded a draft PROM which is ready for refinement and psychometric testing in future quantitative studies. Conclusion: During exacerbation, illness-related emotional distress increases and is multidimensional, acting as a driver for self-management. The preliminary item list with confirmed face validity provides a basis for guiding and evaluating interventions.