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Predictors of HIV Transmission in a US Test-and-Treat Population: 29% in care don't use condoms
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XIX International AIDS Conference, July 22-27, 2012, Washington, DC
Mark Mascolini
More than 1 in 5 HIV-positive people in care in 5 US cities reported inconsistent condom use, according to results of a 5411-person CNICS cohort analysis [1]. From site to site, 5% to 10% of study participants reported unsafe condom use and had a detectable viral low and thus ran a risk of transmitting their HIV to a sex partner. Substance abuse independently raised the odds of being at risk for HIV transmission.
The test-and-treat strategy rests on evidence that earlier detection and treatment of HIV lower viral load in individuals--and in entire communities--and so dampen transmission of the virus [2,3]. But even diagnosed and treated people can transmit their virus if they do not use condoms and if their viral load stays detectable or becomes detectable because of poor adherence or for other reasons. CNICS cohort investigators conducted this analysis to determine the proportion of treated people with a detectable viral load who used condoms inconsistently or not at all.
The study involved HIV-positive patients enrolled in the CFAR Network of Integrated Clinical Systems (CNICS) cohort in five US cities--Birmingham, Boston, San Diego, San Francisco, and Seattle. Cohort members routinely complete a computer-based assessment of behavioral variables including use of drugs, alcohol, or tobacco, sexual risk behaviors, and antiretroviral adherence. The investigators defined being at risk for transmitting HIV as being sexually active and using condoms inconsistently or never in the past 6 months while having a detectable viral load.
The analysis included 13,592 assessments of 5411 people. Age at study entry averaged 44 years, and nadir CD4 count averaged 284. One fifth of study participants (22%) reported inconsistent or no condom use. Rates of detectable viremia with inconsistent or no condom use ranged from 5% to 11% across the 5 study sites and averaged 7%.
Based on these findings, the researchers divided study participant into three groups--3855 people (71%) not at risk for HIV transmission, 1200 people (22%) at risk because of unsafe condom use but with an undetectable viral load, and 356 people (7%) at risk because of unsafe condom use and a detectable viral load.
Women and people older than 50 were significantly less likely to be at risk for transmission than men and younger people (P < 0.001 for both comparisons). At-risk people were significantly more likely to report both past drug use (for example, with cocaine or amphetamines), to report current marijuana use, to report at-risk alcohol use, and to report at-risk injection drug use (P < 0.001 for all comparisons).
A significantly higher proportion of at-risk people had 2 or more sex partners in the past 6 months (54% versus 19%, P < 0.001). Also, a significantly higher proportion of the at-risk group reported having sex after alcohol or drug use in the past 6 months (46% versus 17%, P < 0.001). In the at-risk group, 52% reported never using condoms during vaginal sex in the past 6 months, and 40% reported never using condoms during anal sex in the past 6 months. Proportions of at-risk people who reported using condoms "some of the time" for vaginal and anal sex were 20% and 37%.
Statistical analysis adjusted for age, race, study site, and depression score (determined by a standard test) identified four drug-related habits that independently raised the odds of being at risk for HIV transmission, at the noted odds ratios (OR) and 95% confidence intervals:
-- Past amphetamine use (vs none): OR 1.4 (1.1 to 1.7), P = 0.009
-- Current amphetamine use (vs none): OR 3.5 (2.7 to 4.6), P < 0.001
-- Current crack/cocaine use (vs none): OR 1.5 (1.1 to 2.0), P = 0.008
-- At-risk alcohol use (vs not at risk): OR 1.4 (1.1 to 1.6), P = 0.001
The CNICS researchers suggested that their reliance on self-report to establish risk behavior may underestimate actual risk rates.
"Even patients who have established outpatient HIV care may engage in risky sexual behavior with detectable viremia," the CNICS researchers observed. "Substance use, particularly amphetamines," they added, "may be one important factor" in HIV transmission risk.
The investigators concluded that "test-and-treat policies do not eliminate the need to focus on prevention of potential HIV transmission risk with diagnosed patients in care."
References
1. Crane H, Mimiaga M, Feldman B, et al. Patients in routine HIV clinical care at-risk for potentially transmitting HIV in the 'test-and-treat' era of HIV prevention. XIX International AIDS Conference. July 22-27, 2012. Washington, DC. Abstract THAC0202.
2. Cohen MS, Chen YQ, McCauley M, et al. Prevention of HIV-1 infection with early antiretroviral therapy. N Engl J Med. 201;365:493-505. http://www.nejm.org/doi/full/10.1056/NEJMoa1105243.
3. Montaner JS, Lima VD, Barrios R, et al. Association of highly active antiretroviral therapy coverage, population viral load, and yearly new HIV diagnoses in British Columbia, Canada: a population-based study. Lancet. 2010;376:532-539. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2996043/?tool=pubmed.
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