Practical value of the marker MUC4 for identification of vaginal secretion in penile swabs

Abstract

The mRNA profiling method combined with a reverse transcription endpoint PCR method has been proven to be a suitable technique for the identification of vaginal secretion. The correct identification of a biological source is of vital importance in the samples from sexual assault cases. We have confirmed the reliability of the most common vaginal secretion mRNA-marker MUC4 to detect vaginal secretion in vaginal swabs in 33/42 samples. All negative results were obtained from a woman in menopause. Cross reactivity was detected in 3 out of 52 saliva samples and no cross reactivity (0/10) was detected in samples taken from tonsils. We evaluated the practical value of specificity of MUC4 for the identification of vaginal secretion by testing eight types of penile swabs taken after different sexual intercourses. All samples (5/5) taken from uncircumcised penis after heterosexual sex were positive for MUC4, but only one sample (1/5) from circumcised penis was positive for MUC4. No detection of any marker of interest was observed in penile swabs taken after homosexual anal sex. Additional buccal swabs from tonsils of men and women and penile swabs from clean penis without sex in past two days, were used as a negative control, while markers statherin and histatin 3, specific for saliva, served as positive markers. Both markers STATH and HTN3 were positive (52/52) in those samples as we expected (saliva) and negative in all others (0/92). The paper demonstrates that the correct identification of biological source of samples as vaginal secretion could be possible only if specific markers for saliva are tested coincidently with marker MUC4, while negative results should be taken with great precaution.