# P-287. Real-World Sexually Transmitted Infection (STI) Testing Patterns Among Individuals Using Pre-Exposure Prophylaxis (PrEP) for HIV-1 Prevention in the United States

## TL;DR

This study examines how often people on HIV prevention medication get tested for STIs in the US and finds that while testing increases after starting the medication, most still don't follow the recommended schedule.

## Contribution

The study provides real-world data on STI testing patterns among individuals using PrEP in the US, highlighting gaps in adherence to CDC guidelines.

## Key findings

- STI testing rates increased from 26% before to 47% after starting PrEP.
- Only 33% of PrEP users tested every 6 months as recommended, with 67% testing less frequently or not at all.
- STI prevalence slightly increased from 12% pre-PrEP to 18% post-PrEP, likely due to more frequent testing.

## Abstract

The Centers for Disease Control and Prevention recommends routine sexually transmitted infection (STI) testing every 3–6 months for people taking HIV-1 pre-exposure prophylaxis (PrEP), as part of comprehensive HIV-1/STI prevention services. However, real-world patterns of STI testing among individuals using PrEP in the US remain unclear.Table 1.STI Testing in Adults Newly Prescribed PrEP Within the 12 Month Observation Window Pre- and Post-PrEP InitiationSTI testing and prevalence were assessed 12 months pre- and post-PrEP initiation. STI tests conducted within 15 days of PrEP initiation (before or after) were counted in post-PrEP categories.PrEP, pre-exposure prophylaxis; STI, sexually transmitted infection.Figure 1.Frequency of STI Testing Among Individuals With ≥ 1 STI Test Within the 12 Month Observation Window Pre- and Post-PrEP InitiationSTI tests conducted within 15 days of PrEP initiation (before or after) were counted in post-PrEP categories.a.Included individuals with one STI test only (n = 6435) and individuals with a testing frequency > 9 months (n = 163). b.Included individuals with one STI test only (n = 4537) and individuals with a testing frequency > 9 months (n = 463).PrEP, pre-exposure prophylaxis; STI, sexually transmitted infection.

STI Testing in Adults Newly Prescribed PrEP Within the 12 Month Observation Window Pre- and Post-PrEP Initiation

STI testing and prevalence were assessed 12 months pre- and post-PrEP initiation. STI tests conducted within 15 days of PrEP initiation (before or after) were counted in post-PrEP categories.

PrEP, pre-exposure prophylaxis; STI, sexually transmitted infection.

Frequency of STI Testing Among Individuals With ≥ 1 STI Test Within the 12 Month Observation Window Pre- and Post-PrEP Initiation

STI tests conducted within 15 days of PrEP initiation (before or after) were counted in post-PrEP categories.

a.Included individuals with one STI test only (n = 6435) and individuals with a testing frequency > 9 months (n = 163). b.Included individuals with one STI test only (n = 4537) and individuals with a testing frequency > 9 months (n = 463).

PrEP, pre-exposure prophylaxis; STI, sexually transmitted infection.

Adults (≥ 18 years) newly prescribed any PrEP regimen (October 2020 – December 2023) with ≥ 9 months cumulative use within the 12-months after PrEP initiation, were identified using HealthVerity. Testing and prevalence of chlamydia, gonorrhea, and syphilis were assessed 12 months pre- and post-PrEP initiation. Testing frequency was calculated as the average interval between ≥ 2 tests, categorized as every ≤ 3, > 3 to 6, > 6 to 9, and > 9 months. STI prevalence was defined as an STI diagnosis or positive laboratory result within each 12-month observation window.Figure 2.Mean STI Testing Intervals Among Individuals With ≥ 2 STI Tests in the 12 Month Pre- and Post-PrEP InitiationSTI tests conducted within 15 days of PrEP initiation (before or after) were counted in post-PrEP categories.a.Individuals with unknown sex at birth were excluded.PrEP, pre-exposure prophylaxis; STI, sexually transmitted infection.

Mean STI Testing Intervals Among Individuals With ≥ 2 STI Tests in the 12 Month Pre- and Post-PrEP Initiation

STI tests conducted within 15 days of PrEP initiation (before or after) were counted in post-PrEP categories.

a.Individuals with unknown sex at birth were excluded.

PrEP, pre-exposure prophylaxis; STI, sexually transmitted infection.

Among 42,408 PrEP-naive users, STI testing rates increased from 26% pre-PrEP to 47% post-PrEP initiation; 27% of all PrEP users tested within a 30-day window around PrEP initiation (± 15 days). While 33% of all PrEP users were tested every ≤ 6 months as recommended, 67% were tested every > 6 months or not at all. The proportion of individuals with ≥ 2 tests and the frequency of ≤ 6-monthly testing in these individuals increased post-PrEP use (Table 1). Individuals with commercial insurance, residing in the South or Midwest, or aged ≥ 45 years had the lowest pre-PrEP testing frequencies (Figure 1). After PrEP initiation, testing frequencies remained lowest in the South and among those aged ≥ 45 years, but increased in all other populations to approximately 30% testing every 3 months. Mean testing intervals decreased slightly from 3.8 to 3.7 months pre- and post-PrEP initiation, respectively (Figure 2). STI prevalence increased slightly from 12% pre-PrEP to 18% post-PrEP use, possibly due to increased testing.

Overall, this study suggests that people using PrEP tested for STIs more frequently than before starting PrEP. However, only 33% of PrEP users tested every ≤ 6 months as recommended. As PrEP evolves with less frequent dosing options, further educational and structural interventions are needed to increase adherence with STI testing recommendations.

Xiwen Huang, PhD, Gilead Sciences, Inc.: employee and shareholder Juan Yang, PhD, Gilead Sciences, Inc.: Employee and shareholder Edward Gemson, MS, Gilead Sciences, Inc.: employee and shareholder Wenyi Wang, MS, Gilead Sciences: Employee and shareholder Li Tao, PhD, Gilead Sciences, Inc.: Employee and shareholder Dylan Mezzio, PharmD, Gilead Sciences, Inc.: employee and shareholder Chris Nguyen, PharmD, Gilead Sciences, Inc.: Employee and shareholder Sandra I. McCoy, PhD, MPH, Gilead Sciences, Inc.: employee and shareholder Joshua Gruber, PhD MPH, Gilead Sciences: Employee and shareholder