Objective A prospective, qualitative study was conducted to develop a patient-reported outcome measure (PROM) for daily administration via electronic diary (eDiary) to assess the severity of nosebleeds in patients with hereditary hemorrhagic telangiectasia (HHT), in accordance with Food and Drug Administration (FDA) PROM guidance criteria. Methods Three expert clinicians who treat patients with HHT provided input during instrument development, which comprised: 1) Peer-reviewed literature and instrument review; 2) Development of draft Nosebleed Diary items; 3a) Three rounds of qualitative interviews (two with a paper-based diary, one with an eDiary) with patients with documented severe epistaxis related to HHT, for concept elicitation and cognitive debriefing; 3b) Face validity and translatability assessment; 3c) Patient evaluation of the usability and acceptability of the eDiary device; and 4) Preparation of the final Nosebleed eDiary and conceptual framework. Results No existing instruments were identified that evaluate HHT-related nosebleed severity daily and meet FDA PROM guidance criteria. Frequency, duration, and/or speed of flow (i.e., intensity) were reported by most participants with HHT when asked to describe their nosebleed severity. The Nosebleed eDiary was refined based on 17 patient interviews, clinical expert input and the face validity and translatability assessment. The final four-item eDiary was acceptable to patients with HHT. Conclusion The Nosebleed eDiary is "fit for purpose" to assess the severity of HHT-related nosebleeds, and has established face and content validity. Further adaptation may be required for use in mild or moderate HHT populations. Psychometric testing to evaluate construct validity and reliability are recommended next steps. Level of evidence 2c "Outcomes research".
