Standard Risk-Based Screening Tools Fail to Reliably Predict STI Acquisition Among Persons Using PrEP in New York...

Quarterly sexually transmitted infection (STI) screening is recommended for gay, bisexual, and other men who have sex with men (gbMSM) using HIV pre-exposure prophylaxis (PrEP). However, frequent in-person testing can pose engagement barriers and increase costs, prompting interest in risk-based screening strategies to individualize testing frequency.

We evaluated the extent to which two common sexual risk assessment tools, the I Want the Kit (IWTK) survey and the HIV Incidence Risk Index for MSM (HIRI-MSM), predict bacterial STI acquisition among gbMSM using PrEP. Participants were recruited from a free sexual health clinic in New York City and enrolled in Stick2PrEP2.0 (2018-2020) or Stick2PrEP3.0 (2021-2023). Risk scores were assessed at enrollment and compared with gonorrhea and chlamydia nucleic acid amplification test results at enrollment and during follow-up at three and six months.

Among 298 gbMSM PrEP users, 25% had at least one positive gonorrhea or chlamydia test within one year. Most participants were classified as high-risk by IWTK (53%) or HIRI-MSM (87%). Higher IWTK scores were modestly associated with STI positivity within three months, but neither tool reliably predicted STI acquisition beyond this interval. Low-risk cutoff scores that maintained sensitivity would have applied to only a small minority of participants, limiting clinical utility.

Risk-based screening tools demonstrated limited ability to predict bacterial STI acquisition among gbMSM using PrEP. Reliance on these tools to reduce screening frequency could result in missed STI diagnoses and onward transmission. Until more accurate STI risk models are developed, universal and routine laboratory screening remains essential.