Background:  Co-infection with HIV leads to higher hepatitis C virus (HCV) RNA levels, but the effect of CD4 cell counts and other characteristics of HIV-infected individuals on HCV titres is uncertain. 

Methods:  All HIV/HCV-co-infected individuals in the Swiss HIV Cohort Study (SHCS) with available HCV RNA titres measured by the Roche Amplicor-system and simultaneous (within 1 month) CD4 cell counts before starting anti-HCV therapy were included. Due to the inclusion of censored (upper limit of detection) values for HCV-titres, medians were determined by Kaplan-Meier analysis. Multivariate censored linear regression models, which adjust for censored values, were used to estimate the effects of the different predictors on HCV RNA levels. 

Results:  We included 1023 HIV-infected individuals (66% males, 95% Caucasians, median age 40 years). Of the HCV-measurements, 23% were censored at an upper limit of detection (at 0.5, 0.7, 0.85, or 1x10⁶ log₁₀ IU/mL). Individuals with CD4-cell counts <200/µL had significantly higher HCV titres than those with 200 to 500 and >500 CD4 cells/µL (6.25, 6.08, and 5.98 log₁₀ IU/mL, p = 0.04 and 0.003, respectively). Similarly, individuals with lower nadir CD4 counts had higher HCV titres with every 100-cell increase associated with a 0.06 log₁₀ IU/mL decrease in HCV RNA (p <0.001). Individuals with <200 CD4 cells/µL and detectable (>400 copies/mL) HIV RNA had the highest HCV titres (6.52 log₁₀ IU/mL), followed by those with <200 CD4 and undetectable HIV RNA (6.21 log₁₀ IU/mL), those with >200 CD4 and detectable HIV RNA (6.12 log₁₀ IU/mL), and those with >500 CD4 cells/µL and undetectable HIV RNA (5.92 log₁₀ IU/mL, p = 0.03, 0.005 and 0.001, respectively, for comparison with the first group). Individuals infected with HCV genotype 4 had the lowest HCV titres (5.83 IU/mL), followed by genotype 3, 1, and 2 (6.13, 6.22, and 6.53 log₁₀ IU/mL, p = 0.1, 0.008, and 0.001, respectively, for comparison with genotype 4). The association between CD4 counts and HCV RNA remained significant (p = 0.01) after adjusting for genotypes and HIV RNA. Sex, ethnicity, mode of HIV-transmission, levels of liver enzymes, and presence of hepatitis B antigen were not significant predictors of HCV titres.

Conclusions:  HCV RNA levels were significantly higher in individuals with low CD4 cell counts and detectable HIV RNA and differed markedly between HCV genotypes. However, the absolute differences in HCV titres were small and the clinical relevance of these findings warrants further studies.