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On-Treatment Viral Loads Fell Steadily Since 1997 in Large US-Canadian Analysis: diaparities for Blacks & IDUs
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18th Conference on Retroviruses and Opportunistic Infections, February 27-March 2, 2011, Boston
Mark Mascolini
Viral loads among antiretroviral-treated people in the United States and Canada dropped consistently from 1997 through 2007 to the point where more than half of the study group had an undetectable viral load at the end of follow-up [1]. Disparities in viral suppression rates between blacks and whites persisted through 2007 in this NA-ACCORD analysis, and in 2007 Canadians had a 25% better chance than US residents of attaining an undetectable viral load.
NA-ACCORD combines data from 13 clinical and eight observational HIV cohorts in 17 US states and 4 Canadian provinces. This analysis involved people in the 13 clinical cohorts who had a viral load reading at any point from 1997 through 2007. The researchers defined a viral load below 500 copies as undetectable because of variations in the lower limit of detection over time from cohort to cohort. If a person had more than one viral load measurement in a year, the highest viral load was used for this analysis.
From 1997 through 2007, median viral load rose significantly in people not taking antiretrovirals from 4.24 to 4.71 log (about 17,400 to 51,300 copies, P < 0.01). For the same period, median viral load in treated people fell from 4.12 to 2.70 log (about 13,200 to 500 copies, P < 0.01). The percentage of people taking combination antiretrovirals rose from under 20% in 1997 to almost 57% in 2007. Proportions of people with an undetectable load climbed from 16% in 1997 to 57% in 2007.
Canada did better than the United States in getting its cohort members' median viral load undetectable faster. Canada's median load stood at 4.03 log (about 10,700 copies) in 1997 and hit the undetectable threshold in 2001. The US median load measured 4.14 log (about 13,800 copies) in 1997 and reached the undetectable mark in 2005.
In 1997 an age-adjusted analysis determined that blacks had a 7% lower chance of having an undetectable viral load than whites (odds ratio [OR] 0.93, 95% confidence interval [CI] 0.92 to 0.94) and Hispanics had a 6% lower chance (OR 0.94, 95% CI 0.92 to 0.96). By 2007, blacks had a 10% lower chance of having an undetectable load than whites (OR 0.90, 95% CI 0.89 to 0.92), but Hispanics no longer had a lower chance of attaining undetectability (OR 0.99, 95% CI 0.97 to 1.01).
In 1997 chances of having an undetectable viral load did not differ by country or by HIV transmission risk group. But by 2007 Canadians had a 25% better chance of reaching an undetectable load than US residents (OR 1.25, 95% CI 1.22 to 1.27). Compared with people reporting gay sex as their transmission risk, people reporting heterosexual sex as their transmission risk had a 4% lower chance of being undetectable in 2007 (OR 0.96, 95% CI 0.95 to 0.98) and people reporting injecting drugs as their risk factor had a 10% lower chance (OR 0.90, 95% CI 0.88 to 0.91).
The NA-ACCORD team concluded that "treatment efforts have been successful in reducing viral load." Most people on combination antiretrovirals in these cohorts, regardless of country, now have a viral load below 500 copies.
Reference
1. Althoff K, Rebeiro P, Gill J, et al. Trends in HIV viral load among adults in clinical care in the US and Canada, 1997-2007. 18th Conference on Retroviruses and Opportunistic Infections. February 27-March 2, 2011. Boston. Abstract 548.
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