ORIGINAL ARTICLE Reduction in Neutrophil Count During Hepatitis C Treatment: Drug Toxicity or Predictor of Good Response? Gerardo Alvarez-Uria Æ Jeremy N. Day Æ Anisa J. Nasir Æ Susan K. Russell Æ F. Javier Vilar Received: 17 April 2009 / Accepted: 24 August 2009 Ó Springer Science+Business Media, LLC 2009 Abstract Background Bone marrow suppression is a well-recog- nized toxicity of the treatment of hepatitis C virus (HCV). Reduction of the peginterferon dose because of neutropenia is common in clinical practice. However, reduction of pe- ginterferon dose during the first weeks of HCV treatment is associated with failure to achieve sustained virological response. Aims The objective of this study is to investigate whether the fall of neutrophil count during hepatitis C treatment is associated with achieving sustained virological response. Methods We performed an observational study of patients who completed peginterferon and ribavirin treatment in an Infectious Diseases Department in Manchester, UK. Results Of the 74 patients included in the analysis, 78% had genotype 2 or 3 hepatitis C and 15% had liver cirrhosis. Sustained virological response was achieved in 78% of patients. On univariate analysis, factors related to achieving sustained virological response were younger age, geno- type 2 or 3, baseline neutrophil count, and fall of neutrophil count during treatment. Multivariate analysis showed baseline neutrophil count [ 3.5 9 10 3 cells/mm 3 [odds ratio (OR) 5.7; 95% confidence interval (CI) 1.24–26.3] and a reduction of neutrophil count [ 60% (OR 4.5; 95% CI 1.03– 19.9) to be independently associated with achieving sus- tained virological response. Neutropenia was not associated with an increased risk of infections. Conclusions In this observational study, higher baseline neutrophil count and fall of neutrophil count during the treatment of hepatitis C was associated with achieving sustained virological response. These findings could have important implications for the monitoring and management of HCV treatment with peginterferon if they are confirmed in other studies. Keywords Hepatitis C Á Peginterferon Á Treatment outcome Á Neutropenia Introduction Chronic hepatitis C virus (HCV) infection is a common disease worldwide and is associated with liver cirrhosis and hepatocellular carcinoma [1]. Treatment with peginterferon and ribavirin achieves sustained virological response (SVR) in 40–80% of patients depending on the virus genotype [1]. The mechanism of action of interferon in the treatment of hepatitis C is not fully understood. Its antiviral activity seems to be produced by inducing interferon-stimulated genes, which establish an antiviral specific state within the cell rather than a direct effect on the virus [2]. It is believed that interferon therapies work by similar mechanisms to endogenous interferon, with the greater effectiveness being caused by the higher concentration achieved [3]. A well-recognized dose-dependent side-effect of inter- feron is neutropenia [4]. Combination treatment with ribavirin and peginterferon has higher rates of SVR than G. Alvarez-Uria (&) Á J. N. Day Á A. J. Nasir Á S. K. Russell Á F. J. Vilar Monsall Unit, Department of Infectious Diseases, North Manchester General Hospital, Delaunays Road, Manchester M8 5RB, UK e-mail: gerardouria@gmail.com G. Alvarez-Uria Departament de Medicina, Universitat Autonoma de Barcelona, Barcelona, Spain J. N. Day Oxford University Clinical Research Unit, Hospital for Tropical Diseases, Ho Chi Minh City, Vietnam 123 Dig Dis Sci DOI 10.1007/s10620-009-0969-z