Vaginal secretions are a complex mixture of cells and secretions. There is currently no reliable test to identify material as being from the vagina. Several screening tests based on microscopy have been proposed. Vaginal epithelial cells are large, and many contain glycogen which can be demonstrated by staining with iodine in the form of a solution or exposing to iodine vapor. However, the presence of glycogenated cells is variable depending on the stage of the estrous cycle. Future testing may focus instead on other biochemical factors such as mRNA or microbial signatures.

The most important aspect of vaginal secretions in traditional serology is the presence of markers that are also used to type semen, specifically ABH and PGM1. It is not possible to distinguish grouping results by physiologic origin with an acceptable degree of reliability. This includes situations where the woman is a non-secretor and the man is a secretor. For example, consider a situation where a rape victim is A, sese, and the suspect is A, Se. If absorption-elution testing on the swab shows the presence of group A substance, then the results should be reported with a qualified interpretation since it cannot be discounted that the results came from the victim.

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