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

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. 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/microL from baseline) or concordant response (CD4 count increase >or= 100 cells/microL). 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. 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.