Background:  Infectious complications of interferon (INF)-based hepatitis C virus (HCV) therapy in HIV/HCV co-infection are not well described. The correlation to INF-induced neutropenia is unclear.

Methods:  All recipients of INF-based HCV therapy followed at The Ottawa Hospital Viral Hepatitis Clinic between June 2000 and May 2005 were identified from an SPSS 11.0 clinical database. All infectious complications during the period of interferon exposure and one month after were identified. No patients received G-CSF.

Results:  In total, 214 patients received 246 courses of therapy (6880 person-weeks of therapy); 28 HIV-infected patients received 35 courses of therapy (913 person-weeks of therapy); 11 infectious complications in HIV/HCV patients were recorded (1.2 infections/ 100 person-weeks of therapy), which was similar to HIV-negative patients (1.0 infections/ 100 person-weeks of therapy). The mean time to infection was 10 weeks (17 weeks in HIV negative, p = 0.07). Infections included:  40% respiratory, 16% cutaneous, 15% oral cavity; 12% genitourinary, 12% gastrointestinal; 15% of infections were fungal (thrush 6, cutaneous 4) in nature. The proportion of infection types did not differ between HIV/HCV and HCV. No AIDS-defining illnesses were identified and no infections required hospitalization or discontinuation of therapy in those with HIV. HIV status, age, sex, race, stage and grade of biopsy, and type of INF were not correlated with infection rate by Cox regression analysis. Neutrophil counts declined from a baseline mean of 3800 cells/μL (SD 1700) to a nadir of 1900 cells/μL (SD 1100) by week 8 of therapy. The total, fungal and bacterial infection rates did not correlate with nadir neutrophil count or size of decline from baseline. The total infection rate was not greater for those with nadir counts <1000 cells/μL (0.83/ 100 person-weeks of therapy) or <750 cells/μL (0.71/100 person-weeks). Baseline neutrophil count, nadir count <1000 cells/μL, and occurrence of infectious complication were not related to zidovudine (AZT) use.

Conclusions:  Although the onset may be more rapid in HIV, overall infection rates are similar between HIV/HCV and HCV patients selected for HCV antiviral therapy. Neutrophil count is not correlated with infection rate in recipients of INF-based HCV therapy. INF dose reduction or G-CSF dosing in those with neutropenia is not supported by this analysis.