More than 14,500 people in care in six U.S. clinics spent one quarter of their time with a viral load above 1500 copies.1 A viral load that high raises chances of passing HIV to a sex partner and threatens the HIV-positive person's health. Study groups that spent more than one quarter of their time in care with a viral load above 1500 copies included blacks (26% of time), people 16 to 39 years old (32% of time), and people not taking antiretroviral therapy (58% of time).
HIV-positive people with an undetectable viral load -- below 40 or 50 copies per milliliter of blood -- rarely if ever pass HIV to a sex partner. Research shows that the risk of sexual HIV transmission rises when the viral load stands above 1500 copies.2-4 People with a viral load above 1500 copies usually have not started antiretroviral therapy, started treatment and missed a few doses or stopped entirely, or started an antiretroviral combination that's now failing.
Understanding how often the viral load of HIV-positive people in care stands above 1500 copies can give health authorities a better idea of how many positive people run a risk of passing HIV to their sex partner. Learning which groups of people are more likely to have a viral load above 1500 copies can help health officials and HIV providers work harder to get those people into care and onto steady, effective antiretroviral therapy.
For those reasons, researchers from the Centers for Disease Control and Prevention (CDC) and colleagues at the six U.S. clinics conducted this study to determine how much time HIV-positive people in care spend with a viral load above 1500 copies and how often viral loads are above that level in different HIV groups.
The study involved HIV-positive adults in care in at six clinics in six U.S. cities between April 2009 and March 2013. Everyone had at least two viral load tests during that time, with at least 30 days between the first test and the last test. The researchers called this group the observational cohort. Additional analyses to assess time with a viral load above 1500 copies according to antiretroviral therapy use involved a separate set of HIV-positive people enrolled in a clinical trial at the same six clinics. The researchers called these people the trial participants.
Total observation time for each person started with that person's first viral load test and ended with the last viral load test. The researchers calculated the percentage of time with a viral load above 1500 copies by determining the viral load between each pair of tests, in this manner:
Next the CDC team divided observational cohort patients into several groups according to (1) percentage of viral load pairs with more than 6 months between the first and second, (2) years of entry into the analysis (2009-2010, 2010-2011, 2011-2012), (3) whether the first viral load was above 1500 copies, (4) age, (5) race/ethnicity, (6) sexual orientation, (7) injection drug use as an HIV exposure factor, (8) health insurance status, and (9) clinic site. For the trial participants, the researchers divided patients into groups according to (1) antiretroviral therapy status at entry to the study, (2) study group in the trial these people were participating in, (3) new or established patient, and (4) clinic site.
Finally, the research team used standard statistical methods to compare these groups according to time with a viral load above 1500 copies.
The main study group (the observational cohort) included 14,532 HIV-positive people with two or more viral load measurements. About one third of this group was gay or bisexual men, another third heterosexual men, and another third women. Only 13% of study participants had injection drug use as a risk factor for becoming infected with HIV.
About one third of the group was 16 to 39 years old, one third 40 to 49, and one third 50 to 85. While 64% of study participants were black, 18% were Hispanic, and 17% white. More than 90% of these people had prescriptions for antiretroviral therapy during the 3 years from 2010 through 2012. About 15% of study participants had private insurance, 15% used Medicare, 25% used Medicaid, and the rest relied on Ryan White funding or charity. (Ryan White funding supports care for low-income, uninsured, and underinsured people with HIV and their families.)
Median observation time for the group (time between first and last viral load result) was 1073 days (almost 3 years), and study participants had a median of 9 viral load measures. Viral loads stood above 1500 copies an average 23% of the time per person, or 84 days per year per person.
Percentage of observation time with a viral load above 1500 copies varied a good deal across the different subgroups analyzed: Groups with the most time spent above the 1500-copy mark were those whose first viral load stood above 1500 copies (Figure 1), people for whom more than 25% of consecutive viral loads were measured more than 6 months apart (Figure 1), people whose CD4 count lay below 350 when their viral load was first measured (Figure 1), people 16 to 39 years old versus older (Figure 2), blacks versus whites (Figure 2), women and heterosexual men versus gay men (Figure 2), people who injected drugs (Figure 3), and people who did not have private insurance (Figure 3).
Figure 1. In a study of 14,532 adults with HIV and at least two viral load measures, percentage of time spent with a viral load (VL) above 1500 copies varied by (1) whether the first viral load measured was above or below 1500 copies (two left bars), (2) percentage of viral load pairs measured more than 6 months parts (three middle bars), and (3) CD4 count at the first viral load measure (two right bars).
Figure 2. A study of 14,532 U.S. residents with at least two viral load measures found that the percentage of time they spent with a viral load above 1500 copies varied by (1) age (three left bars), (2) race/ethnicity (three middle bars), and (3) sex and sexual orientation (three right bars). Htx, heterosexual; MSM, men who have sex with men.
Figure 3. In a large study of U.S. HIV patients who had at least two viral load measures, percentage of time spent with a viral load above 1500 copies varied by injection drug use (IDU) status (two left bars) and type of health coverage (four right bars).
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