Examination of various mirna markers in the differentiation of menstrual blood from peripheral blood

Body fluids such as peripheral blood, menstrual blood, semen, saliva, and vaginal secretions are the most significant biological samples commonly found at the scene of a crime. These provide decisive clues to help qualitatively analyse a criminal case, restructure the crime scene, and provide strong evidence for the courtroom. Similarly, the distinction between menstrual blood and peripheral blood is vital for forensic casework, as it could provide strong evidence to figure out the nature of some criminal cases. In this study, the relative expression levels of five different miRNAs (miR-451, miR-144, miR-205, miR-214, and miR-203) were analysed by SYBR green-based real-time PCR with 96 samples from 5 different body fluids, including 21 peripheral blood, 21 menstrual blood, 20 saliva, 13 semen, and 21 vaginal secretions. Then, it was investigated whether menstrual blood could be distinguished from peripheral blood with candidate markers selected by discriminant function analysis performed with SPSS 22.0. In the first step, delta CT values of miR451 were selected as the dependent variable, and blood and non-blood samples were selected as the independent variables to distinguish blood samples from non-blood samples. As the second step, two different paths were followed. The first was to select miR-214, miR203, and miR205 as independent variables and MB and PB as dependent variables to distinguish peripheral blood from menstrual blood. The other way was to select only miR203 from the miRNAs as an independent variable. The first of the two function test sets used was named Z1 and Z2, to separate blood samples from non-blood samples, and the second set, named Y1 and Y2, was used to separate menstrual blood from peripheral blood. The two-step method was followed, and a 100% accuracy rate was achieved when 21 test samples were used. This success was valid in the second step both when miR-214, miR-203, and miR-205 were used as variables and when only 203 was used as a variable. These results indicated that miR451 and miR203 would be sufficient to distinguish single source blood from menstrual blood and could be used successfully in the analysis of forensic cases. Since results can be obtained with 5 ng of RNA in the study, it is possible to use it in small amounts in forensic samples.