Article Text

P3.242 Factors associated with vaginal prostate-specific antigen detection and self-reported unprotected sex in a clinical trial in malawi
  1. Yasaman Zia1,
  2. Nicole Davis1,
  3. Jeffrey Wiener1,
  4. Donna Lapple2,
  5. Lameck Chinula3,
  6. Jennifer Tang3,
  7. Gerald Tegha3,
  8. Albans Msika3,
  9. Marcia Hobbs2,
  10. Athena Kourtis1
  1. 1Centres for Disease Control (CDC), Atlanta, GA, USA
  2. 2University of North Carolina (UNC), Chapel Hill, NC, USA
  3. 3UNC-Project Malawi, Lilongwe – Malawi


Introduction Vaginal prostate-specific antigen (PSA) is a biomarker of recent semen exposure that may overcome potential fallacies of self-reported sexual behaviours, improving sexual exposure assessment in HIV/STI research.

Methods We conducted a cohort study to compare PSA detection and self-reported unprotected sex using data from a clinical trial in Malawi that randomised 73 HIV-infected and 24 HIV-uninfected women to depot medroxyprogesterone acetate injectable or levonorgestrel implant. Women were advised to abstain from vaginal intercourse or use a condom the day preceding study visits. We tested 539 vaginal swabs from 97 women for PSA using the ABAcard p30 rapid strip test (Abacus Diagnostics, Inc., West Hills, CA). Self-reported sexual behaviours and vaginal swabs were collected at six study visits. Log-binomial regression with generalised estimating equations were used to estimate associations of PSA detection and reported unprotected sex with demographic and behavioural factors, adjusting for study arm and pre- vs. post-contraception initiation.

Results Overall, 55 (57%) women tested positive for PSA and 54 (56%) women reported unprotected sex. Among PSA-positive samples, 62% (65/105) of instances reported no unprotected sex. The following were associated with PSA detection: HIV-negative status (Prevalence Ratio (PR): 1.69, 95% Confidence Interval (CI):1.09, 2.61), younger age (PR: 1.04, CI: 1.00, 1.08), reported unprotected sex (PR: 2.48, CI: 1.70, 3.60), and sex within past 48 hours (PR: 4.68, CI: 3.00, 7.30). The same factors were significantly associated with self-reported unprotected sex, as was PSA detection (PR: 2.45, CI: 1.7, 3.53).

Conclusions Self-reported sexual behaviours were significantly associated with PSA detection. However, PSA was detected among women reporting no unprotected sex, suggesting misreporting of condom use or condom failure. HIV-negative status and younger age were associated with unprotected sex, suggesting more frequent biases in research data for these groups based on social desirability and non-adherence to protocols.

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