HIV-positive youth are less likely than adults to achieve viral suppression on antiretroviral treatment

While adolescents and young adults are about as likely as older people to be linked to care after being diagnosed with HIV in the United States, less than a third were retained in care or started antiretroviral therapy (ART). Only 7% reached undetectable viral load, much lower than the rate for older individuals, researchers reported at the Eighth International AIDS Society Conference on HIV Pathogenesis, Treatment, and Prevention last month in Vancouver. Prompt referral to youth-friendly services, however, increased the likelihood of viral suppression.

Bill Kapogiannis of the US National Institute of Child Health and Human Development and fellow investigators with the SMILE Collaborative looked at the HIV continuum of care for young people with HIV. SMILE (Strategic Multisite Initiative for the Identification, Linkage and Engagement in Care of Youth with Undiagnosed HIV Infection) is a collaboration between the Adolescent Medicine Trials Network for HIV/AIDS Interventions (ATN), the US Health Resources and Services Administration (HRSA) and the Centers for Disease Control and Prevention (CDC).

The continuum or cascade of care refers to the sequence of steps from HIV testing and diagnosis, to linkage into care, to starting treatment, to achieving viral suppression. Public health researchers track progress in addressing the epidemic by looking at how many people 'get lost' or fall out of care at each step.

Approximately a quarter of all new HIV infections in the US occur among youth aged 13-24 years, the researchers noted, yet there are little youth-specific data on engagement in care.

The CDC estimates that 86% of the 1.2 million people living with HIV in the US have been tested and know their status, falling to 49% among youth age 18-24, according to 2011 figures reported in the November 28, 2014 Morbidity and Mortality Weekly Report.

The SMILE study started at the next step of the continuum, looking at outcomes among 1548 youth, age 12-24, who were diagnosed with HIV and identified by the collaboration between October 2012 and September 2014. Among the 733 participants with available data, 81% were male, 72% were black, 70% identified as gay or bisexual, the mean age was 20.6 years and the mean CD4 T-cell count was 463 cells/mm³.

The researchers determined the number of participants who were referred to care, linked to care (within 42 days after referral), engaged in care (defined as at least one additional visit within 16 weeks after linkage), retained in care (at least one additional visit within 52 weeks of engagement) and achieved viral suppression or undetectable plasma HIV RNA.

Of the 1548 total participants diagnosed with HIV, 1053 (68%) were newly linked to care. Of these 839 participants (80%) were engaged in care, and among those 473 (56%) were retained in care. Looked at as proportions of the initial total diagnosed with HIV – not just those who had reached the previous step in the continuum – 54% were linked to care, 31% were retained in care, 31% started ART and 7% achieved undetectable viral load.

Among the 358 people who were not successfully linked to care, the main reasons were repeated failure to attend appointments (34%), inability to locate the participant (32%), participant's refusal of care (11%) and being out of the service jurisdiction (11%).

At the time of linkage to care, 38% of participants had a CD4 count above 500 cells/mm³, 29% had 350-500 and 34% had less than 350. As participants reached successive steps of the care continuum median viral load decreased progressively, while the proportion with undetectable HIV RNA increased.

Significant predictors of viral suppression in an adjusted analysis included lower viral load at the time of linkage to care, recent ART use (adjusted hazard ratio [HR] 3.10, or more than 3-fold higher) and a shorter interval between testing and referral for linkage to care (adjusted HR 1.64 for 0-7 days, 2.52 for 7 days to 6 weeks and 2.08 for 6 weeks to 3 months, compared to more than 3 months).

The 7% viral suppression rate seen in this analysis is surprisingly low – substantially lower than the approximately 40% figure for all age groups combined in the CDC's Medical Monitoring Project (according to the July 2015 Supplemental Surveillance Report).

"The SMILE collaborative has demonstrated that HIV-infected youth had high levels of plasma viremia and advanced infection at diagnosis, which have implications for disease progression and transmission potential," the researchers concluded. "While they linked to care at similar rates as adults, youth achieved disproportionately low rates of virologic suppression."

"Prompt referral to youth-friendly linkage-to-care services after HIV testing is an independent predictor of viral load suppression," they continued. "Recent developments affecting the urgency to start antiretroviral treatment for HIV-infected persons have direct implications for youth who would now have even less time for adjustment to their new diagnosis. This argues for more research and services to address such critical issues of treatment readiness and medication adherence among newly infected youth."