Sensitive real-time polymerase chain reaction (RT-PCR) assays have an HIV RNA detection limit below 1 copy/mL of plasma. Factors that raise chances of reaching a completely undetectable viral load are not well understood.

To address that question, researchers in Toulouse, France, studied 1392 people with a viral load below 50 copies/mL for at least 1 year while taking combination antiretroviral therapy. For this cross-sectional analysis, the researchers divided this population into three groups: 479 people (34%) with a completely undetectable viral load (group 1), 617 people (44%) with a viral load of 1 to 20 copies/mL (group 2), and 296 people (21%) with a viral load of 20 to 50 copies/mL (group 3).

Statistical analysis comparing groups 1 and 2 identified three factors that raised the odds of having a completely undetectable viral load at the time of the study, at the following odds ratios (OR) (and 95% confidence intervals):

• Highest-ever viral load below 100,000 copies/mL: OR 1.51 (1.15 to 1.99), P = 0.003 • Current CD4 count below 500 cells/μL: OR 1.44 (1.08 to 1.92), P = 0.01 • Viral load below 50 copies/mL longer than 2 years: OR 2.32 (1.20 to 4.54), P = 0.01

Statistical analysis comparing groups 1 and 3 identified three factors that raised the odds of having a completely undetectable viral load at the time of the study:

• Highest-ever viral load below 100,000 copies/mL: OR 2.48 (1.75 to 3.50), P < 0.001 • Viral load  below 50 copies/mL longer than 1 year: OR 3.33 (1.66 to 6.66), P = 0.0006 • NNRTI-based regimen: OR 1.45 (1.03 to 2.04), P = 0.03

Individual NNRTIs did not affect chances of attaining a completely undetectable viral load.

The Toulouse team suggests that “this routinely used RT-PCR assay may prove to be a valuable tool in further large-scale studies.”

By Mark Mascolini

Source: G. Martin-Blondel, K. Sauné, V. Vu Hai, B. Marchou, P. Delobel, J. Izopet, L. Cuzin, P. Massip. Factors associated with a strictly undetectable viral load in HIV-1-infected patients. HIV Medicine. 2012; 13: 568-573.

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