Standard Risk-Based Screening Tools Fail to Reliably Predict STI Acquisition Among Persons Using PrEP in New York City: Implications for Universal STI Screening in PrEP Care.
Max Flanagan, Elijah D. LaSota, et al. • Sexually Transmitted Diseases • 2026
Risk-based screening tools demonstrated limited ability to predict bacterial STI acquisition among gbMSM using PrEP, and reliance on these tools to reduce screening frequency could result in missed STI diagnoses and onward transmission.
Key Findings
Results
A substantial proportion of gbMSM PrEP users tested positive for gonorrhea or chlamydia within one year of enrollment.
Among 298 gbMSM PrEP users, 25% had at least one positive gonorrhea or chlamydia test within one year.
Participants were recruited from a free sexual health clinic in New York City.
STI testing was conducted via nucleic acid amplification tests (NAAT) at enrollment and at three and six months follow-up.
Study enrollment spanned two cohorts: Stick2PrEP2.0 (2018-2020) and Stick2PrEP3.0 (2021-2023).
Results
The majority of participants were classified as high-risk by both standard risk assessment tools, limiting their discriminatory value.
53% of participants were classified as high-risk by the I Want the Kit (IWTK) survey.
87% of participants were classified as high-risk by the HIV Incidence Risk Index for MSM (HIRI-MSM).
The high proportion classified as high-risk means the tools identify most of the population as needing frequent screening, providing little individualization.
Both tools were assessed at enrollment and compared with subsequent STI test results.
Results
Higher IWTK scores were only modestly associated with STI positivity within three months, and neither tool reliably predicted STI acquisition beyond this interval.
The modest association between IWTK scores and STI positivity was limited to the three-month window.
Neither IWTK nor HIRI-MSM demonstrated reliable predictive ability for STI acquisition at six months or beyond.
Risk scores were assessed at enrollment and compared with gonorrhea and chlamydia NAAT results at enrollment, three months, and six months.
HIRI-MSM showed no reliable predictive association with STI acquisition at any follow-up interval examined.
Results
Low-risk cutoff scores that maintained adequate sensitivity applied to only a small minority of participants, limiting the clinical utility of risk-based screening strategies.
Cutoff scores designed to preserve sensitivity for STI detection would have classified only a small minority of participants as low-risk.
This finding means that even optimally applied risk thresholds would reduce screening in very few individuals.
The limited proportion eligible for reduced screening substantially restricts the potential cost savings or engagement benefits of a risk-based approach.
The authors concluded that these tools have limited clinical utility for individualizing STI screening frequency in gbMSM PrEP users.
Background
Quarterly STI screening is recommended for gbMSM using PrEP, but frequent in-person testing poses engagement barriers and increases costs, motivating interest in risk-based individualization of testing frequency.
Current guidelines recommend quarterly STI screening for gay, bisexual, and other men who have sex with men (gbMSM) on PrEP.
Barriers to frequent in-person testing include cost and patient engagement challenges.
Interest in risk-based screening strategies is driven by the goal of individualizing testing frequency to reduce these barriers.
The two tools evaluated—IWTK and HIRI-MSM—are described as 'common sexual risk assessment tools.'
Conclusions
The authors conclude that universal and routine laboratory STI screening remains essential in PrEP care until more accurate risk prediction models are developed.
Reliance on current risk-based tools to reduce screening frequency 'could result in missed STI diagnoses and onward transmission.'
The conclusion explicitly states that 'until more accurate STI risk models are developed, universal and routine laboratory screening remains essential.'
The findings have implications for both clinical practice and public health policy around PrEP care delivery.
The study population was drawn from a free sexual health clinic in New York City, which may reflect a higher-risk urban population.
What This Means
This research suggests that two commonly used questionnaire-based tools designed to assess sexual risk—the I Want the Kit (IWTK) survey and the HIV Incidence Risk Index for MSM (HIRI-MSM)—are not reliable enough to determine how frequently gay, bisexual, and other men who have sex with men (gbMSM) taking HIV prevention medication (PrEP) should be tested for bacterial sexually transmitted infections (STIs) like gonorrhea and chlamydia. The study followed 298 PrEP users in New York City over six months and found that one in four participants tested positive for gonorrhea or chlamydia at least once. While one tool showed a weak association with STI diagnoses within three months, neither tool could reliably predict who would acquire an STI over a longer period.
A key practical problem identified is that both tools classified the vast majority of participants as 'high risk'—87% by one tool and 53% by another—leaving almost no one eligible to be identified as lower risk and potentially screened less frequently. Even when the researchers tried to set thresholds that would catch most STI cases, only a tiny fraction of participants would qualify for reduced testing. This means using these tools to cut back on testing frequency would likely cause many infections to go undetected.
This research suggests that current risk assessment questionnaires are insufficient substitutes for routine, scheduled STI testing in PrEP care. Reducing testing based on these tools could lead to missed diagnoses and ongoing spread of STIs in the community. The authors emphasize that universal quarterly STI screening should remain standard practice for gbMSM on PrEP unless and until better predictive tools are developed.
Max Flanagan, Elijah D. LaSota, Simian Huang, Joshua Klein, T. Y. Kim, Caroline Carnevale, et al.. (2026). Standard Risk-Based Screening Tools Fail to Reliably Predict STI Acquisition Among Persons Using PrEP in New York City: Implications for Universal STI Screening in PrEP Care.. Sexually Transmitted Diseases. https://doi.org/10.1097/OLQ.0000000000002395