Discordant responses on starting highly active antiretroviral therapy: suboptimal CD4 increases despite early viral suppression in the UK Collaborative HIV Cohort (UK CHIC) Study *

Objectives Patients starting highly active antiretroviral therapy (HAART) may have a suboptimal CD4 increase despite rapid virological suppression. The frequency and the significance for patient care of this discordant response are uncertain. This study was designed to determine the incidence of a discordant response at two time‐points, soon after 6 months and at 12 months, and to determine the relationship with clinical outcomes. Methods Data obtained in the UK Collaborative HIV Cohort Study were analysed. A total of 2584 treatment‐naïve patients starting HAART with HIV viral load (VL)>1000 HIV‐1 RNA copies/mL at baseline and <50 copies/mL within 6 months were included in the analysis. Patients were classified at either 6–10 (midpoint 8) months or 10–14 (midpoint 12) months as having a discordant (CD4 count increase <100 cells/μL from baseline) or concordant response (CD4 count increase ≥100 cells/μL). Results Discordant responses occurred in 32.1% of patients at 8 months and in 24.2% at 12 months; 35% of those discordant at 8 months were concordant at 12 months. A discordant response was associated with older age, lower baseline VL, and (at 12 months) higher baseline CD4 cell count. In a multivariate analysis it was associated with an increased risk of death, more strongly at 12 months [incidence rate ratio (IRR) 3.35, 95% confidence interval (CI) 1.73–6.47, P <0.001] than at 8 months (IRR 2.08, 95% CI 1.19–3.64, P =0.010), but not with new AIDS events. Conclusions Discordant responders have a worse outcome, but assessment at 12 months may be preferred, given the number of ‘slow’ responders. Management strategies to improve outcomes for discordant responders need to be investigated.