HEPATITIC C VIRUS

Oliver Kimka Ndimbie, M.D., Medical Director, Patient Viral Testing

INTRODUCTION

Hepatitis C virus (HCV) appears to be the major cause of parenterally transmitted non-A, non-B hepatitis.  It is believed to be responsible for more than 150-170,000 cases of hepatitis annually.  Approximately 50% of these patients are at risk of developing chronic complications including chronic active hepatitis, cirrhosis, and possibly hepatocellular carcinoma.  The virus responsible for this infection has been isolated and an antibody test, based on the ELISA reaction, has been developed and licensed.  Intravenous drug abusers who share needles, dialysis patients, and persons exposed to blood or blood products are susceptible to this virus.

Anti-HCV testing is now routine in blood and organ donation.  This has resulted in a reduced incidence of transfusion-associated hepatitis (TAH) thereby increasing the safety of blood and blood products.  In cases of accidental exposure to this blood borne pathogen, immune serum globulin administration may provide protection.  Histopathological evaluation for viral hepatitis has improved with the advent of testing for HCV.  Recent studies report that alpha interferon therapy may have a beneficial effect on some HCV infected patients (NEJM; 321:1501-6; 1989).

diagnosis

The main weakness of the ELISA test remains its high rate of false positive reactions.  This problem is complicated by the fact that a licensed confirmatory test is not currently available.  However, a presumptive diagnosis of HCV infection can be made on the basis of clinical and laboratory findings.  A positive ELISA test associated with an elevation of the serum alanine aminotransferase (ALT) or SGPT in an individual with a history of parenteral drug use or exposure to blood products is highly suggestive of this infection.  Of patients with chronic non-A, non-B hepatitis who undergo biopsy within 5 years after onset, approximately 40% will have histologic evidence of chronic active hepatitis or cirrhosis.  Many of these patients have no clinical manifestations.

donor blood safety

Prior to the institution of specific antibody testing, the incidence of TAH due to non-A non-B hepatitis was reduced by 40-60% by careful screening and the use of surrogate markers such as the ALT.  The addition of anti-HCV testing has further reduced this incidence.  At present, the incidence of post-transfusion non-A non-B hepatitis has been estimated to be 1-4% of transfusion recipients.

donor counselling

The prevalence of elevated ALT and anti-HCV in the U.S. donor pool is 4.3% and 1% respectively.  Persons who test positive are deferred from further donations.  These donors are notified and instructed to seek medical evaluation.  The clinician should ascertain possible risk factors for HCV infection, to repeat testing if necessary and to recommend sequential evaluation and therapy if needed.  A specific counseling objective is to advise against sharing blood contaminated household items.  The risk of sexual transmission is low (MMWR 40:RR-4; 1991).

patient testing

The patient Viral Testing Laboratory of Central Blood Bank performs over 700 anti-HCV patient tests each month.  In this pre-selected high-risk population, approximately 15% of the samples are repeatedly reactive.  To assist in the differentiation of acute and chronic HCV disease, ALT should be concurrently evaluated; enzyme levels are elevated in acute inflammation.  At present, there is no licensed confirmatory test for HCV.  However, the recombinant immunoblot assay (RIBA) appears useful in identifying infected patients with chronic liver disease (Ann Intern Med  114:1010-12; 1991); this test is available upon request.  Persons who are accidentally exposed to HCV contaminated material may not seroconvert for up to 12 months (average is 4 months).  Bimonthly follow-up is recommended for one year or until seroconversion.

Copies of the Transfusion Medicine Update can be obtained by contacting Deborah Small at (412) 209-7320 or
by e-mail:  dsmall@itxm.org.