Validation of Breast Idea Volume Estimator Application in Transfeminine People.

Background: Accurate estimation of breast volume is important as researchers aim to achieve optimal feminization for transfeminine people. The Breast Idea Volume Estimator (BIVE) application allows estimation of breast volume using two-dimensional (2D) photographs but has not been validated in the chests of people who have undergone testosterone-mediated puberty. Methods: To estimate breast volume, clinical photographs and 3D scans were collected at baseline and 6 months, as a prespecified secondary outcome of a randomized clinical trial of antiandrogen therapy in transfeminine people commencing hormone therapy. BIVE was used to estimate breast volume by two independent researchers and compared with the gold standard of 3D scan calculated volume at different timepoints. Statistical analysis was performed, including the mean absolute difference, standard error of measurement, and intraclass correlation, to determine accuracy, precision, and interrater agreement. Results: Clinical photography and 3D scans were collected from 82 breasts of 41 participants. The median (interquartile range) age of participants was 25 (22-28) years, and the median (interquartile range) body mass index was 24.6 (21.2-28.9) kg/m Conclusions: BIVE provided an accurate, precise, and reliable measure of breast volume in the chests of people who have undergone testosterone-mediated puberty, compared with the gold standard of 3D scan.