The Centers for Disease Control and Prevention’s (CDC) sexually transmitted infection (STI) testing guidelines for people on Truvada (tenofovir/emtricitabine) as pre-exposure prophylaxis (PrEP) may lead health care providers to miss a significant proportion of asymptomatic STIs.
The prevailing wisdom among the public health community is that routine screening for STIs among people on PrEP can mitigate the effects of any extra sexual risk-taking such individuals may undertake after starting Truvada, by reducing the amount of time during which they may pass on such infections. Considering this, an increase in testing frequency could help further reduce the risk of STI transmission to others among people on PrEP.
Researchers in the SPARK, a community-based PrEP demonstration project conducted at Callen-Lorde Community Health Center the largest LGBT health center in New York City, studied 280 people who started PrEP and analyzed their STI data for the six months before they started PrEP and the 12 months following the start of Truvada. The study’s lead, Sarit Golub, MPH, PhD, a psychologist at Hunter College in New York City presented findings at the 2016 Conference on Retroviruses and Opportunistic Infections (CROI) in Boston.
Current CDC guidelines for PrEP recommend screening for STIs only every six months, unless an individual reports symptoms of a possible infection. (The CDC recommends assessing for symptoms for STIs every three months among those on PrEP.) Meanwhile, the CDC’s 2015 STI treatment guidelines recommend that men who have sex with men (MSM) receive STI screening every three to six months, emphasizing the importance of testing among those with a history of such infections.
“Testing and treatment is critical, both for PrEP patients themselves, and for their partners,” Sarit Golub said at CROI. “We need to change these guidelines now, beucase it is much harder to tell providers to change their practices once they’ve started it. ”
In the SPARK study, individuals on PrEP are screened every three months for urethral and rectal gonorrhea and chlamydia, as well as for syphilis. Participants also visit the clinic for STI testing and treatment in between their quarterly clinic visits if they experience symptoms of a possible STI.
Twenty-one percent of the participants (58 people) had an STI during the six months before starting PrEP, including 11 percent who tested positive for such an infection at their first clinic visit for a Truvada prescription. At the three-month follow-up visit, 13 percent of the participants were diagnosed with STIs, with 77 percent of these cases (or 10 percent of all participants) identified through routine screening, as opposed to an individual coming in to the clinic as a result of symptoms. In other words, these 77 percent of cases would have been missed if the clinic had followed the CDC guidelines for STI testing among those on PrEP.
Thirty-three percent of the individuals diagnosed with STIs at the three-month follow-up visit had a history of an STI diagnosis that would have triggered screening under guidelines that focus on diagnosis history.
At the nine-month follow-up visit, 15 percent of the participants were diagnosed with STIs, with 68 percent of these cases (10 percent of all participants) diagnosed as a result of routine screening (not recommended by the CDC at the nine-month visit), as opposed to screening based on reported symptoms.
The percentage of participants with repeat STI diagnoses increased over time. Even so, the researchers concluded that basing STI screening on an individual’s diagnosis history at the nine-month visit would have missed 16 percent of the STI cases.
Throughout the 12-month study period, following CDC STI screening guidelines for people on PrEP would have delayed diagnosis and treatment for 24 percent of the participants (increasing the amount of time during which they may pass such an infection on to others), including 40 cases of rectal STIs and three cases of syphilis.
The researchers stressed that “STI screening may be particularly important at the first three-month follow-up visit. Routine STI testing at each PrEP prescription visit appears warranted, with particular attention to those with past STI history.”
STI diagnosis rates at the initial visit and the three-, six-, nine- and 12-month follow-ups were a respective 11 percent, 13 percent, 21 percent, 15 percent, and 13 percent. Golub said that there was anecdotal evidence at this point, based on conversations between counselors and the members of the study, that the participants engaged in higher sexual risk-taking between the first and second quarterly follow-up visits, when compared with pervious visits. Golub theorized, based on those conversations, that the study participants may have wanted to wait until the end of the first three-month period on PrEP before they felt they could have faith in Truvada as HIV prevention; and once they felt more confident, they perhaps felt more comfortable engaging in a higher level of sexual risk. After the six-month point, they may have then reverted to their initial level of sexual risk-taking. Golub stressed that as a group, the members of this study already used condoms at low rates before starting PrEP.