Testing Cytological Adequacy and Insertion Depth for Anal Self-Sampling: A Pilot Intervention Study

Anal cancer screening consensus guidelines were released in 2024. Although anal cytology and high-risk human papillomavirus (HPV) tests are currently performed in a clinic by a healthcare provider, there is increasing interest in providing individuals with the option to collect a sample themselves. Our objective was to compare the performance characteristics and acceptability of a swab inserted at two different depths for anal cytology self-sampling.

We recruited sexual and gender minority individuals to complete anal cytology self-sampling and a survey. Participants were randomized to either a 3- or 5-cm insertion depth, then given a demonstration and a kit to complete onsite in a private bathroom. Cytopathology and reflex HPV testing were conducted.

Fifty individuals completed anal cytology self-sampling and a post-swab survey, with 23 participants randomized to the 5-cm insertion depth and 27 participants randomized to the 3-cm depth. Although not significant, the proportion of cytologically adequate specimens was higher with a 5-cm insertion (87.0%, 95% CI 66.4%-97.2%) compared to a 3-cm insertion (70.4%, 95% CI 49.8%-86.2%). A higher proportion of specimens collected squamocolumnar junction cells with the 5-cm insertion depth (47.8%, 95% CI 26.8%-69.4%) compared to the 3-cm insertion (29.6%, 95% CI 13.8%-50.2%) though this difference was non-significant. Acceptability was high and not associated with insertion depth.

Swabs inserted 5 cm for anal cytology self-sampling collected a non-significantly higher proportion of cytologically adequate and squamocolumnar junction cells compared to 3 cm, with no difference in acceptability.

ClinicalTrials.gov: NCT07085845.