The CDC said it would not change its long-standing recommendation on how frequently to test men who have sex with men for HIV.

The agency has recommended since 2006 that U.S. providers offer HIV screening to all sexually active MSM “at least annually.” Since then, some experts have argued that MSM — the group at highest risk for HIV infection — might benefit from being screened more frequently.

The CDC said a literature review turned up insufficient evidence to change the recommendation but that “Clinicians can also consider the potential benefits of more frequent HIV screening (e.g., every 3 or 6 months) for some asymptomatic sexually active MSM based on their individual risk factors, local HIV epidemiology, and local policies.”

Researchers from the CDC’s Division of HIV/AIDS Prevention detailed the process of revisiting the agency’s 2006 recommendation in MMWR. The CDC estimated in 2014 that 15% of patients living with HIV in the U.S. were unaware of their infection.

“HIV testing in the critical first step in making HIV-infected persons aware of their status, so that they can obtain treatment and prevent transmission of HIV,” the researchers wrote.

A CDC work group of epidemiologists, clinicians, behavioral scientists, health policy experts and health economists reviewed nearly 6,500 abstracts from studies published in Australia, Canada, New Zealand, Western Europe and the U.S. Among them, 111 were reviewed in full and rated for outcome, but only 13 met the criteria to be evaluated for the study, according to the researchers.

They judged the overall quality of these 13 studies to be “low.”

“Eleven studies addressed health or economic benefits of more frequent screeningcompared with annual screening. Eight of these were mathematical models that the CDC work group classified as having low suitability because of uncertainty about the validity of the parameter estimates and questions about the models’ generalizability,” the researchers wrote. “Two studies addressed intervals between HIV screening or diagnostic tests in clinical settings but did not directly address the acceptability of more frequent than annual HIV screening among asymptomatic MSM. No studies addressed harms associated with, or the feasibility of, conducting more frequent HIV screening in clinical settings in the United States.”

The CDC work group asked 24 external experts to consult on the results, including clinicians, epidemiologists, academic researchers, health department policy and program staff members and members of the MSM community. Most of these outside experts “believed the literature was insufficient to conclude that more frequent screening had demonstrated benefits over annual screening but that the scientific and programmatic evidence suggested that some MSM would be willing to be screened more frequently,” according to the report.

The report said more research is needed to establish factors that might increase the risk of HIV infection for MSM and merit more frequent screening.

“For MSM who are prescribed pre-exposure prophylaxis, HIV testing every 3 months and immediate testing whenever signs and symptoms of acute HIV infection are reported is indicated,” the researchers wrote. “MSM who experience a specific high-risk sexual exposure or have symptoms of recent HIV infection should seek immediate HIV testing, and clinicians should be alert for the symptoms of acute HIV infection and provide appropriate diagnostic testing.”– by Gerard Gallagher