Objective: The purpose of this study is to evaluate the dose response relationship between absolute neutrophil count (ANC) and the development of infection in patients being treated with pegylated interferon and ribavirin for chronic hepatitis C (HCV). Design: The design is a cohort study utilizing retrospective chart review. Population, Sample, Setting, Years: Subjects were selected from the population at a Hepatitis Clinic in an academic medical center between June 2000 and December 2001. The sample includes 65 HCV patients who have completed at least 24 weeks of pegylated interferon subcutaneously and rivavirin therapy. Concepts: The association between neutropenia and risk of infection has been examined in a number of retrospective studies with cancer chemotherapy patients. The current guidelines in the cancer chemotherapy patients call for discontinuation of interferon therapy for ANC levels <1500/mL due to the risk of infection. Similarly, an ANC <1000/mL has been identified as a risk factor for bacteremia in patients with human immunodeficiency virus (HIV) infection while controlling for CD4+ lymphocyte count. Currently no studies were located on the relationship between neutropenia and infection in HCV patients. However, the guidelines for treatment of HCV patients with pegylated interferon and ribavirin allow the ANC to drop as low as 500/mL before discontinuation of therapy. Methods: This cohort study has a sample of 65 HCV patients being treated with pegylated interferon alfa-2b 1.5 mcg/kg subcutaneously each week and ribavirin capsules by mouth twice each day. Each patient has completed at least 24 weeks of therapy with complete blood counts (CBC) and physical examinations performed a minimum of every 4 weeks during therapy. Cases of infection have been determined by reviewing the office visit notes, telephone log and medications ordered. Infections have been classified as oral, skin, upper respiratory, pneumonia, and other. Levels of neutropenia have been classified as <500/mL, 500-999/mL, 1000-1499/mL, 1500-2000/mL, and >2000/mL. Analysis: ANC stratum-specific rates of infection will be calculated by site of infection and any infection. Linear trend tests will be performed to assess the dose-response relationship between neutropenia and rates of infection. Conclusions: Evaluation of the association between ANC and infection in the HCV patient on pegylated interferon and ribavirin therapy is needed to determine appropriateness of current guidelines for dose reduction. Guidelines for use of cell line stimulants to increase ANC in the prevention of infection can also be further developed.
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