Characterizing Self-Reported Daily Diary Epistaxis Measures in Hereditary Hemorrhagic Telangiectasia.

To characterize a proposed clinical trial outcome measure of weekly cumulative bleeding duration from daily nosebleed diaries, termed PRO‐CB (patient‐reported outcome of cumulative bleeding). We also assessed cumulative weekly gushing bleeding duration (PRO‐CGB) and evaluated the accuracy of patient recall on Epistaxis Severity Score (ESS) items 1–3 compared with daily diary data. In this prospective observational study at the Toronto HHT Centre (St. Michael's Hospital, Unity Health Toronto), 23 patients from two clinical trials were observed during three‐month run‐in periods. Participants recorded each nosebleed episode daily, noting duration and intensity (gushing vs. non‐gushing). Data were analyzed using linear mixed‐effects models, correlation tests, and partial autocorrelation analyses. Diary compliance was 98.8%. Mean weekly PRO‐CB was 71.2 min (SD 81.1); mean episode duration was 5.9 min (SD 12.6). Daily and monthly means were 10.1 min (SD 20.1) and 307.6 min (SD 311.6), respectively. Gushing episodes lasted significantly longer than non‐gushing (mean difference: 5.81 min; 95% CI: 4.53–7.09). Bleeding patterns varied widely across individuals. PRO‐CGB also showed inter‐patient variability. PRO‐CB and ESS total scores were not significantly correlated ( p = 0.18, r = 0.39). ESS items 1 and 2 correlated strongly with diary data ( p < 0.001); item 3 did not. Agreement was 83% for item 1% and 70% for items 2 and 3. Daily nosebleed diaries are a feasible and accurate tool for tracking epistaxis severity in HHT. Despite inter‐patient variability, PRO‐CB offers a meaningful outcome measure for epistaxis clinical trials. 2 Keywords: epistaxis, HHT, patient‐reported outcomes