Prevalence of occult hepatitis C virus in patients with HCV-antibody positivity and serum HCV RNA negativity

Introduction and aim
Chronic hepatitis C infection is a global problem with an increasing burden on healthcare, particularly in Egypt. Even with the advent of highly sensitive techniques, a subset of patients with positive hepatitis C virus antibody (HCV-Ab) and negative HCV-viremia remain challenging to treat. Therefore, we tried to determine the prevalence of occult HCV infection (OCI) in peripheral blood mononuclear cells (PBMCs) of patients presenting with a positive serologic test for anti-HCV-Ab and negative serum HCV-RNA-PCR (spontaneously cleared patients) and followed up those patients.
Patients and methods
Between March 2010 and March 2015, a prospective study was designed to include all consecutive patients with HCV-Ab positivity and HCV-RNA negativity who attended the Assiut Unit for treatment of viral hepatitis - the National Committee for Control of Viral Hepatitis. A total of 25 patients were recruited. Spontaneous clearance of serum HCV infection was approved on the basis of HCV-Ab positivity using two third-generation enzyme-linked immunosorbent assay tests and serum HCV RNA negativity on three consecutive occasions, each 6 months apart. Follow-up serum HCV RNA levels were evaluated for patients with OCI every 6 months. The RNA extraction step was performed by a protocol modified from that of the QIAamp viral RNA kits. Blood samples for separation of PBMCs were collected from all patients. PBMCs were obtained using Ficoll-Hypaque density gradient of EDTA anticoagulated blood according to the manufacturer's instructions (Lymphoflot). Detection of HCV viral load was performed with the kit supplied by Applied Biosystem (HCV RT-PCR Kit lot No.).
Results
A total of 25 patients (21 men, mean age 36.2 ± 9.1) cleared HCV spontaneously (HCV-Ab positive and serum HCV RNA negative). Genomic HCV RNA was detected in PBMCs of three (12%) of 25 patients. These three patients with OCI were followed up for 18 months by measuring their serum HCV RNA using highly sensitive real-time PCR every 6 months. Only one patient became overt HCV with a low level of viremia.
Conclusion
OCI was detected in a considerable prevalence in patients who cleared HCV spontaneously, that entails corporations of HCV-viral assay in PBMCs into the diagnostic algorithm.