Vaginal swab specimen processing methods influence performance of rapid semen detection tests: a cautionary tale

Abstract

Background: Detection of semen biomarkers in vaginal fluid can be used to assess women's recent exposure to semen. Quantitative tests for detection of prostate-specific antigen (PSA) perform well, but are expensive and require specialized equipment. We assessed two rapid immunochromatographic strip tests for identification of semen in vaginal swabs.

Study design: We tested 581 vaginal swabs collected from 492 women. Vaginal secretions were eluted into saline, and PSA was measured using the quantitative IMx (Abbott Laboratories, Abbott Park, IL, USA) assay. Specimens were also tested using the ABAcard p30 test (Abacus Diagnostics, West Hills, CA, USA) for detection of PSA and RSID-Semen test (Independent Forensics, Hillside, IL, USA) for detection of semenogelin (Sg).

Results: Vaginal swab extraction using saline was compatible with direct assessment of vaginal swab eluates using ABAcard for PSA detection, but not for Sg detection using RSID. The rapid PSA test detected 91% of specimens containing semen compared to 74% by the rapid Sg test.

Conclusion: Investigators are urged to optimize vaginal swab specimen preparation methods for performance of RSID or other tests to detect semen components other than PSA. Previously described methods for PSA testing are not uniformly applicable to other tests.