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  52nd ICAAC Interscience Conference on
Antimicrobial Agents and Chemotherapy
September 9-12, 2012, San Francisco
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Over 10% With Persistent Low-Level Viremia Have Virologic Failure Within Year
  52nd ICAAC, September 9-12, 2012, San Francisco

Mark Mascolini

More than 10% of Swiss HIV Cohort Study (SHCS) participants with persistent low-level viremia (3 consecutive loads between 21 and 400 copies) had virologic failure (viral load above 400 copies) within a year [1]. But no one with very low-level viremia (21 to 49 copies) had a virologic failure.

Causes and consequences of a low but detectable viral load remain hard to nail down despite frequent study in the past decade. SHCS investigators tried to shed more light on this question in a case-control study involving 179 people with persistent low-level viremia and 5389 controls with a viral load always below 20 copies.

Case patients had a viral load below 20 copies for at least 24 months with antiretroviral therapy, then a load between 21 and 400 copies on 3 or more consecutive plasma samples with at least 8 weeks separating the first and last sample. No one changed their antiretroviral regimen during that period. Controls had 3 consecutive viral loads below 20 copies through at least 32 weeks without changing their regimen. This retrospective analysis involved patients seen from January 2000 through December 2010.

The 179 cases were slightly but significantly older than the 5389 controls (average 46 versus 44 years, P = 0.03). About 70% in each group were men and a little over 80% were Caucasian. Proportions of men who have sex with men, heterosexuals, and injection drug users were also consistent among cases and controls at about 40%, 40%, and 20%. A significantly higher proportion of cases than controls had a nadir CD4 count below 200 (70% versus 62%, P = 0.01). Average treatment duration was slightly but significantly shorter in cases (2.7 versus 3.1 years, P = 0.01).

Fewer cases than controls took nonnucleoside-based regimens. In multivariate analysis, taking a protease inhibitor regimen (compared with a nonnucleoside combination) raised the odds of persistent low-level viremia 85% (odds ratio [OR] 1.85, 95% confidence interval [CI] 1.06 to 3.23, P = 0.03). Taking an all-nucleoside regimen boosted the odds more than 8 times (OR 8.37, 95% CI 3.54 to 19.8), P < 0.001).

Nineteen of 155 people with persistent low-level viremia (12%) went on to virologic failure within 48 weeks. Two factors tended to raise the odds of virologic failure in multivariate analysis. Diabetes upped the odds almost 9 times (OR 8.83), though that association did not reach statistical significance (95% CI 0.66 to 118.84, P = 0.1). Suboptimal adherence also predicted virologic failure (OR 3.66), but again the association fell short of statistical significance (95% CI 0.95 to 14.04, P = 0.06).

Twenty-six people had very low-level viremia, defined as a viral load detectable between 21 and 49 copies. None of these people had a virologic failure during the study period.

Among people with persistent low-level viremia, records showed that 115 (64% of 179) did not intensify their antiretroviral regimen and 51 (28%) did. People taking a nucleoside-only combination and those entering the cohort in 2009 or 2010 (when more new antiretrovirals rapidly became available) were more likely to intensify their regimen.

Among the 115 people who did not intensify their regimen, 12% had virologic failure within 24 weeks, compared with 9% in the intensification group, a nonsignificant difference (P = 0.8). While 33% who did not intensify their regimen regained an undetectable viral load within 24 weeks, 63% who did intensify regained an undetectable load, a highly significant difference (P = 0.001).


1. Boillat Blanco N, Darling K, Schoni-Affolter F, et al. Persistent low-level viraemia in HIV-1-infected patients: Swiss HIV Cohort Study. 52nd Interscience Conference on Antimicrobials and Chemotherapy (ICAAC). September 9-12, 2012. San Francisco. Abstract H-1566.