HIV Rebound Risk May Be Predicted by Baseline Viral Load, Time to Viral Suppression
A patient's baseline viral load when starting HIV treatment is significantly correlated with his or her chances of achieving viral suppression -- as well as his or her risk of subsequent viral rebound, according to study results presented at EACS 2013 in Brussels, Belgium.
The study results suggest that a patient's viral load could help predict how well the patient will respond to treatment. Moreover, those patients with a higher baseline viral load who took longer to reach viral suppression were more likely to experience a viral rebound.
The study, presented by Laura Waters of the Research Department of Infection and Population Health at University of College London, analyzed clinic data from 2000 to 2011 on 8,184 treatment-naive patients with HIV, all of whom started treatment more than three months after their diagnosis. First-line treatment involved either a protease inhibitor (PI)-based or non-nucleoside reverse transcriptase inhibitor (NNRTI)-based regimen.
Of the initial 8,184 patients, 7,475 individuals (91.3%) eventually achieved viral suppression; these patients were included in the analysis by Waters et al. Their median age was 38, and 80.3% were male. Sixty-four percent were white and 25.5% were black. Mode of transmission was classified as 65% via homosexual intercourse and 28.6% heterosexual intercourse. The median baseline CD4+ cell count was 245 cells/mm3. About 24% started treatment with a PI-based regimen and 76% with an NNRTI-based regimen.
Patients were stratified into one of four groups according to baseline viral load: less than 10,000 copies/mL (22.5% of the patients), between 10,000 and 100,000 (42.4%), between 100,000 and 500,000 (30.3%) and over 500,000 (4.8%).
In terms of how many months it took to reach viral suppression (defined as a viral load below 50 copies/mL), 42% took less than three months, 39.5% took three to six months, 14.7% took six to 12 months and 4.5% took over 12 months. The median time to viral suppression was 3.5 months.
The percentage of each group that achieved viral suppression was higher among participants with a lower baseline viral load. Among participants with a baseline viral load less than 10,000 copies/mL, 91.9% achieved suppression, compared to 92% with between 10,000 and 100,000 copies/mL, 90.7% with between 100,000 and 500,000 copies/mL, and 87.4% with over 500,000 copies/mL. A logrank test for the differential yielded a P value of less than .0001, Waters said.
After achieving viral suppression, 1,289 patients (17.1%) subsequently experienced viral rebound, with 415 (5.6%) rebounding within one year of suppression. Patients who had a higher baseline viral load and who took longer to achieve viral suppression were more likely to rebound, Waters said.
Ultimately, those with a baseline viral load between 100,000 and 500,000 copies/mL had a 34% increased risk of experiencing viral rebound compared to those with a baseline viral load less than 100,000 copies/mL, Waters said. This increased risk was even more pronounced -- 67% higher -- for those with a baseline viral load over 500,000 copies/mL.
Overall, with these results, Waters et al concluded that patients with a high baseline viral load should be monitored closely, even after achieving an undetectable viral load, as they have a higher risk of viral rebound.