Progression of Platelet Counts in Treatment Naïve HIV/HCV Co-Infection

Background: Previous research has suggested an association between infection with hepatitis C virus (HCV) or with human immunodeficiency virus (HIV) and low platelet counts. This study estimates platelet count changes over time in HIV/HCV co-infected participants and compares them with the changes in platelet count among HIV mono-infected participants to test if HIV/HCV co-infection is associated with lower platelet counts. Methods: This retrospective cohort study included all HIV treatment naive patients from four sites in the Centers for AIDS Research Network of Integrated Clinical Systems (CNICS) cohort with platelet count measurements between 2002 and 2009. We conducted a mixed effects linear regression modeling the mean change in platelet count per year while adjusting for age, sex, race, baseline CD4 cell count, and site. Index date was the first platelet count after 2002, and participants were censored upon initiation of treatment for HIV or HCV. Results: There were 929 HIV/HCV co-infected and 3558 HIV mono-infected participants with a mean follow-up time of 1.2 years. HIV/HCV co-infected participants had on average a slighter lower platelet count at baseline (234,040 vs. 242,780/μL; p-value = 0.004), and a more rapid mean reduction per year (7230 vs. 3580/μL; p-value < 0.001) after adjusting for age, sex, baseline CD4 count. Conclusions: In treatment naive participants, HIV/HCV co-infection is associated with a more rapid decline in platelet count compared with HIV mono-infection.