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Steady Drop in Time Spent With Viral Load Above 1500 Copies in US Group
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Conference on Retroviruses and Opportunistic Infections (CROI), February 13-16, 2017, Seattle
Mark Mascolini
People in clinical care for HIV spent 37% of the time with a viral load above 1500 copies in 2000, but that proportion dropped to 10% in 2014, according to a large Centers for Disease Control and Prevention (CDC) analysis [1]. The CDC team believes this decline suggests a falling risk of HIV transmission from people in care for their infection in the United States.
The investigators observe that most cases of sexual HIV transmission involve positive partners with a viral load above 1500 copies. Research indicates that HIV-positive people who fall out of care account for 61% of US HIV transmissions [2]. The CDC team hypothesized that time spent with a viral load above 1500 copies dropped over recent years in the United States because of improving antiretroviral regimens and a move away from treatment interruptions.
To test that hypothesis, the investigators charted viral loads over time in the HIV Outpatient Study (HOPS), starting with the first viral load recorded on or after January 1, 2000 and ending with the last viral load recorded on or before December 31, 2014. Study participants made at least 2 HOPS visits and had at least 2 viral load measures at least 30 days apart during the study period. The primary outcome was percent of person-time with a viral load above 1500 copies, calculated as each person's number of days with a viral load above 1500 relative to the total number of observation days for that person. The researchers used generalized estimating equations to calculate this outcome, as well as trends per year in five 3-year periods (2000-2002, 2003-2005, 2006-2008, 2009-2011, 2012-2014)
The analysis involved 5873 people with a median follow-up of 5.4 years. The group spent 86% of observation time on antiretroviral therapy (ART). During the study period, these people spent 74% of their time on ART with a viral load at or below 1500 copies, 13% of their time on ART with a load above 1500, 9% of their time not on ART with a viral load above 1500, and 4% of their time not on ART with a viral load at or below 1500. Cohort members had a median of 15 viral load measures collected every 3.6 months.
Percent of time with a viral load above 1500 copies fell over the study period, dropping from 37% in 2000 to 10% in 2014 (P < 0.01). With the analysis restricted to people on ART, time with a viral load above 1500 copies waned from 32% in 2000 to 7% 2014 (P < 0.01).
Overall, the study group spent 24% of the observation period with a viral load above 1500. That proportion was higher in people under 35 years old (32%) than in 35- to 49-year-olds (24%) and people 50 or older (16%). Women spent more time with a 1500-plus load than men (31% versus 22%), and blacks spent more time above 1500 (33%) than Hispanics (24%), whites (20%), or other racial/ethnic groups (19%). Percent of time above 1500 copies also differed by HIV risk (heterosexual female 31%, heterosexual male 26%, men who have sex with men 21%), insurance status (public 31%, private 21%), and baseline ART status (naive 29%, experienced 23%). Over the 5 study periods, percent of time above 1500 copies dropped steadily in people taking a protease inhibitor regimen, a nonnucleoside regimen, an integrase inhibitor regimen, or any other regimen.
In multivariable regression analysis,* every later calendar year was associated with lower percent time spent above 1500 copies (adjusted rate ratio [aRR] 0.91, 95% confidence interval [CI] 0.90 to 0.91). In the same analysis, 7 factors were independently associated with more percent time above 1500 copies:
-- Baseline viral load above 1500: aRR 2.25, 95% CI 2.10 to 2.41
-- Baseline CD4 count below 350 (vs 500+): aRR 1.16, 95% CI 1.09 to 1.24
-- No ART (vs on ART): aRR 3.48, 95% CI 3.30 to 3.67
-- Younger than 35 (vs 50+): aRR 1.50, 95% CI 1.36 to 1.65
-- 35 to 49 years old (vs 50+): aRR 1.35, 95% CI 1.23 to 1.48
-- Public insurance (vs private): aRR 1.24, 95% CI 1.17 to 1.32
-- Black (vs white): aRR 1.19, 95% CI 1.12 to 1.27
The researchers suggest earlier ART and improved regimens contribute to the falling proportion of time spent with a viral load above 1500 copies. They call for continued efforts to address time spent above 1500 copies in identified risk groups, including younger people, blacks, people who rely on public insurance, and people with higher baseline viral load or lower baseline CD4 count.
*In the multivariate regression analysis, calendar year and ART use are time-updated, while all other variables are measured at baseline.
References
1. Buchacz K, Mendoza M, Armon C, et al. Time spent with HIV viral load >1500 copies/mL among patients in HIV care, 2000-2014. Conference on Retroviruses and Opportunistic Infections (CROI), February 13-16, 2017, Seattle. Abstract 32.
2. Skarbinski J, Rosenberg E, Paz-Bailey G, et al. Human immunodeficiency virus transmission at each step of the care continuum in the United States. JAMA Intern Med. 2015;175:588-596.
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