Validation Study of a Photo-Based Menstrual Blood Loss Metric.

OBJECTIVE: To validate an objective photo-based electronic method of quantifying menstrual blood loss against the current gold standard alkaline hematin method. METHODS: In this multicenter, prospective cohort study, 79 participants (33 in the training phase, 46 in the validation phase) 18-50 years of age who were premenopausal with self-reported heavy menstrual bleeding were recruited from February to November 2023. Participants provided demographic and medical history details at baseline and then used study-provided pads, photo mats, and smartphones to capture images of menstrual blood loss per pad in one menstrual cycle. A photo-based smartphone application used image analysis software to convert the surface area of blood staining on each menstrual pad into menstrual blood loss volume. The outcome measures were menstrual blood loss per pad and per cycle measured in milliliters, with the alkaline hematin method as the reference standard. Bland-Altman analysis was used with 46 participants from the validation phase to construct limits of agreement between the photo-based and alkaline hematin methods for measuring menstrual blood loss. The sensitivity and specificity of the photo-based method for diagnosing heavy menstrual bleeding (menstrual blood loss more than 80 mL per cycle) were also evaluated. RESULTS: The photo-based method correlated strongly with the alkaline hematin reference standard for both per-pad (R 2=0.75) and per-cycle (R 2=0.83) blood loss. Agreement was high, with minimal bias and limits of agreement within clinically acceptable ranges. For identifying heavy menstrual bleeding, the method achieved 100.0% sensitivity, 93.5% specificity, and 100.0% negative predictive value. CONCLUSION: A photo-based method provides a valid, practical, and accessible alternative to the alkaline hematin standard, enabling accurate diagnosis and monitoring of heavy menstrual bleeding in both clinical and research settings.