Abstract PS7/3
The Impact of Baseline Viral Load (VL) and Time to Viral Suppression on Treatment Responses to First-line Combination Antiretroviral Therapy (cART) Print
S. Jose1, L.J. Waters2, S. Edwards2, P. Benn2, C. Sabin1, UK CHIC
1UCL Research Department of Infection and Population Health, London, United Kingdom, 2Mortimer Market Centre, London, United Kingdom
Background: Modern trials show non-significant differences in virological response by baseline VL. We investigated the impact of baseline VL and time to viral suppression on risk of subsequent rebound.
Eligible subjects were ART-naïve individuals with viral suppression (< 50 copies/ml) on first-line cART (2 NRTI plus PI +/- ritonavir or NNRTI) from Jan 2000-June 2011 in the UK CHIC study. Kaplan Meier and Cox Proportional Hazards models were used to investigate effect of baseline VL and time to suppression on risk of rebound (2 consecutive VL>50 copies/ml).Covariates considered for inclusion in multivariable models were: baseline CD4, regimen class (un-stratified analyses), NRTI backbone, prior AIDS, hepatitis C co-infection, age, sex, ethnicity, exposure.
Results: 7,475 patients were included, 20.7% female, 64.0% white. Initial ART was NNRTI-based in 76.4%. Median (IQR) CD4 count at baseline was 245 (178-324) cells/mm3 and 22.5%, 42.4%, 30.3% and 4.8% had baseline VL< 10,000, 10,000-100,000, 100,000-500,000 and >500,000 copies/ml respectively. Median (IQR) time to viral suppression was 3.5 (2.3-5.3) months.Those commencing cART with lower VL acheived viral suppression sooner (p< 0.0001). 1289 (17.1%) patients experienced viral rebound; 415 (5.6%) within one year of suppression. Those with higher baseline VL were more likely to experience rebound as were those who took longer to achieve viral suppression. Baseline VL of 100,000-500,000 and>500,000 copies/ml were associated with a 34% (95% confidence interval: 1.17-1.54) and 67% (1.34-2.08) increased risk of rebound respectively over reference (< 100,000 copies/ml) after adjustment.
We show, in patients who achieve an undetectable VL on first-line cART, an increased risk of viral rebound in those who take longer to suppress and those with a high baseline VL. There was no significant difference between choice of third agent. We recommend that patients with high baseline VL should continue to be monitored closely, even after virological suppression, as they remain at higher risk of rebound.

Assigned speakers:
Dr Laura Waters , Mortimer Market Centre , London , United Kingdom

Assigned in sessions:
18.10.2013, 10:30-12:30, Parallel Session, PS7, Antiretroviral Therapy II, Bozar (Plenary Hall)