Beyond waste: menstrual blood as a powerful diagnostic tool for women's health.

Menstrual blood (MB), once thought of as nothing more than biological waste, has now come to be regarded as a noninvasive and low-cost diagnostic tool with great potential for women's health research and clinical use areas. MB is a complex and diverse biofluid that represents the state of the female reproductive system, as it consists of endometrial, immune, and stem cells, the vascular components, and biomolecules, all reflecting the physiological and pathological state of the female reproductive system. The latest scientific evidence shows that MB has already taken up its diagnostic role in a number of disorders, such as endometriosis, cervical cancer, genital and reproductive tract infections, metabolic-endocrine imbalances, and even systemic diseases. Technology advancements have bundled up the digital droplet ELISA, next-generation sequencing, and wearable in-pad biosensors that altogether supported the improvement of sensitivity, specificity, and access to MB-based diagnostics. The aforementioned innovations make it possible to carry out real-time monitoring, self-sampling at home, and long-term tracking of women's reproductive health, which thus diminishes the reliance on invasive diagnostic methods and fosters patient-centered healthcare. Yet, there are some significant limitations that still exist, for example, the lack of standardization for collection and preservation protocols, the limited number of large-scale validation studies, and inter-individual biological variability. In conclusion, MB is an unparalleled, biological specimen that is still largely unexamined and hence can lead to breakthrough advancements in the fields of early disease detection, personalized medicine, fertility evaluation, and women's participation in healthcare innovations. MB diagnostics can open up new avenues for precision medicine and women's health equity by changing the perception of waste to be something that gives insights into wellness, as well as the corresponding acceptance of waste as the main parameter used in women's health.