Evaluation of recently developed methods for the forensic detection of menstrual blood

Body fluid identification is an important aspect of forensic work, as it can help identify a suspect and provide information about the kind of criminal activity that took place. Blood is one of the most commonly found body fluids at a crime scene. While visually it is easily distinguishable from other fluids, an accurate method is needed to differentiate between peripheral blood and menstrual blood. This differentiation could provide critical evidence regarding consent in an alleged sexual assault. The presence of peripheral blood indicates a traumatic cause, whereas menstrual blood points towards a natural bleeding cause. Accurate detection of menstrual blood can also help with the reconstruction or corroboration of events. Menstruation is the shedding of the internal lining of the uterus that occurs on a monthly basis in women of a reproductive age group. Menstrual blood is different in composition from the peripheral blood flowing through arteries and veins. It consists of a mixture of vaginal and cervical secretions, epithelial cells, debris from the endometrial lining, blood and fibrinolytic products. The fibrinolytic products are associated with the prevention of blood clot formation. Several methods have been researched and used for the detection of menstrual blood. These include microscopy, identification of the lactate dehydrogenase isoenzyme, detection of fibrinolytic products, and profiling of messenger ribonucleic acid (mRNA) and micro RNA (miRNA). Even though menstrual blood is encountered at crime scenes, a reliable routine procedure for its identification has not yet been incorporated in forensic laboratories. In this study, four methods of detection of menstrual blood were evaluated and compared with each other regarding efficacy. These methods are the LGC ParaDNA® Body Fluid ID Test, SERATEC® PMB Test, DIMERTEST® Latex Assay and Microscopic methods using Lugol’s Iodine and Dane’s staining method. The LGC ParaDNA® Body Fluid ID Test identifies menstrual blood by detecting the mRNA marker MMP10. The SERATEC® PMB Test and DIMERTEST® Latex Assay both detect D-dimers present in menstrual blood. In addition, the SERATEC® PMB Test can detect the presence of peripheral blood. Microscopic identification is performed by identifying vaginal epithelial cells present in the menstrual blood. Menstrual blood samples were self-collected from six anonymous donors on three consecutive days of menses on either a cotton swatch or a cotton swab. Samples from the earliest day were tested in triplicate using the first three methods. For the fourth method, Lugol’s Iodine and Dane’s stain were applied to various cell types to test the utility of the stains. The ParaDNA® Body Fluid ID Test, SERATEC® PMB test and the DIMERTEST® Latex Assay all show promise for the detection of menstrual blood in forensic samples. None of the tests showed a cross reactivity to the other body fluids tested, but some ParaDNA® and DIMERTEST® samples yielded a false negative result for menstrual blood or peripheral blood. The SERATEC® PMB Test outperformed the other methods, both in sensitivity and accuracy. It was accurate for all samples, with a short run time and minimal training required. Microscopic detection of menstrual blood via detection of vaginal epithelial cells could not be accurately investigated as Dane’s staining method could not be reproduced and the presence of blood obscured the results for the Lugol’s method