(P333-LB) Home Testing Goes Extra-Genital: The Potential for Expanding NAAT STI Home Testing Programs to Include Self-Collected Throat and Rectal Swab Specimens

Background

The “I Know” (dontthinkknow.org) home testing program has been implemented in eleven CA counties, including Los Angeles County (LAC), to expand chlamydia and gonorrhea testing access for young cisgender women and transgender men, through distribution of free self-collection kits. Clients mail self-collected vaginal swab specimens to a Public Health Lab (PHL) for Aptima Combo 2 assay testing. Due to lack of validation for extra-genital testing, “I Know” has been limited to vaginal testing. LAC Department of Public Health worked with the Los Angeles LGBT Center and LetsGetChecked to assess the use of self-collected rectal and throat swab specimens to expand case-finding through “I Know” and other STI home testing programs.

Methods

Patients attending the LA LGBT Center clinic for STI clinical care or screening were offered $40 gift cards to participate in the study. Each study participant had a self-collected swab specimen paired with a staff-collected swab specimen from the throat and/or rectum. All specimens were sent by courier to the LAC PHL, and then tested on the Hologic Panther. Results for patient-collected specimens were compared with results for staff-collected specimens; equivocal and discordant results were re-tested once.

Results

A total of 160 throat specimen pairs and 166 rectal specimen pairs were collected in 2022, with analysis completed March 2023 (Table 1). Throat specimens had 140 concordant negative pairs (i.e., paired results matched), 14 concordant positive pairs, and 5 persistent discordant pairs. Overall concordance was 154/160 (96.3%). Rectal specimens had 137 concordant negatives, 24 concordant positives and 5 persistent discordant pairs. Overall concordance was 161/166 (97%). From a disease control perspective that assumes all positives are significant, relative sensitivity for infection detection was 94.7% (18/19 positives) for patient-collected throat specimens and 96.6% (28/29 positives) for patient-collected rectal specimens.

Conclusions

Both throat and rectal self-collected specimens were highly effective at detecting STI infections. Based on these results, LAC PHL determined that self-collected throat and rectal specimens are acceptable using the Aptima Combo 2 assay on the Panther platform. This paves the way for offering at-home extra-genital testing to at-risk populations, including cisgender and transgender women and men and non-binary individuals, across all sexual orientations.