A study published in the journal BMJ Sexual & Reproductive Health on August 7 is the first to compare the absorption of period products using human blood, finding that diaphragm-shaped menstrual discs may be better than pads or tampons at absorbing menstrual flow.
"Manufacturers of period products have previously used saline or water to measure how absorbent they are. Menstrual blood, however, is much thicker than water, and contains endometrial tissue, mucus and other secretions, and is therefore absorbed at a different rate, according to the paper.
“No study exists comparing the capacity of currently available menstrual hygiene products using blood,” the study’s authors wrote. “Utilizing actual menstrual blood to test the collection capacity of menstrual hygiene products would be challenging, but blood products are a closer approximation than water or saline.”"
There might be studies that used blood far in the past for no longer used period products. But no modern product study seems to have used actual blood, just water, saline, or occasionally a liquid solution with other components added to it, such as hemoglobin.
There appears to be no industry standard for such testing except for tampons.
NIST needs to step up their game.