An unusual case of false positive hepatitis C infection

Hepatitis C virus (HCV) is a leading cause of death from liver disease worldwide. The diagnosis of HCV infection is usually made with a positive HCV antibody test and a subsequent positive molecular test that detects the presence of HCV RNA. The interpretation of anti- HCV values that are close to laboratory cut-offs can be challenging. We present a bizarre case of a woman who converted her HCV antibody status during her intensive care unit (ICU) hospitalization. A 78-year-old Caucasian woman was admitted to our ICU after surgery for strangulated abdominal hernia. The HCV antibody test at admission was negative. Her post-operative course was complicated with surgical site infections and entero-enteral fistulas, so she underwent three more surgeries. After the last surgery a vacuum- assisted closure (VAC) device was placed (Fig. 1). During this period she received a total of 9 units of packed red blood cells to treat anemia induced by the surgical procedures. Two months after her admission she was transferred to the step down unit. A new HCV antibody test was then routinely ordered that was positive with a signal-to-cutoff ratio (S/CO) of 3.52. A recombinant immunoblot assay (RIBA) was performed for confirmation and came also positive. In order to rule out the unlike event of a mislabeled sample we retested the patient for anti-HCV a few days later. The result was again positive (S/CO 3.58) and RIBA was undetermined. At that time the patient had no signs of liver disease and her aminotransferase levels were within normal limits. We ordered an HCV core antigen test and an HCV-RNA quantitative test. The antigen test was negative and the HCV-RNA was undetectable (<20 IU/ ml). We therefore considered that the reactive HCV antibody test and RIBA were false positive.