HCV Assays 

Hepatitis C virus (HCV) assays are used to evaluate for HCV infection.

Category

HCV assays

Device details

HCV antibody assays include the following:

• Abbott Laboratories - Abbott HCV EIA 2.0
• OraSure Technologies - OraQuick HCV Rapid Antibody Test
• Ortho-Clinical Diagnostics - ORTHO HCV Version 3.0 ELISA, VITROS Anti-HCV assay
• Roche Diagnostics - Elecsys Anti-HCV assay

HCV RNA qualitative assays include the following:

• Chiron - PROCLEIX HIV-1/HCV Assay
• Roche Molecular Diagnostics - COBAS Amplicor HCV Test (v2.0), COBAS Ampliprep/COBAS Amplicor HCV Test (v2.0), COBAS Ampliscreen HCV Test (v2.0)
• Siemens Healthcare Diagnostics - Versant HCV RNA Qualitative Assay

HCV RNA quantitative assays include the following:

• Abbott Molecular - RealTime HCV
• Roche Molecular Diagnostics - COBAS Ampliprep/COBAS TaqMan HCV Test, COBAS TaqMan HCV Test (v2.0) for use with the High Pure System
• Siemens Healthcare Diagnostics - Versant HCV RNA 3.0 Assay (bDNA)

HCV genotyping assays include the following:

• Roche Molecular Diagnostics - LINEAR ARRAY Hepatitis C Virus Genotyping Test (Europe only; not approved by the US Food and Drug Administration [FDA])
• Siemens Healthcare Diagnostics - Trugene HCV Genotyping Assay (research use only), Versant HCV Genotype 2.0 Line Probe Assay (research use only)

Currently, 2 hepatitis C virus (HCV) enzyme immunoassays (EIAs) are approved by the US Food and Drug Administration (FDA) for clinical use: Abbott HCV EIA 2.0 and ORTHO HCV Version 3.0. These assays are 99% specific but cannot distinguish acute from chronic infection. The most recent third-generation EIA detects antibodies against core protein and nonstructural proteins 3, 4, and 5 and can yield positive results an average of 8 weeks after the onset of infection.

Two other serologic assays are FDA-approved: VITROS Anti-HCV , an enhanced chemiluminescence immunoassay (CIA), and Elecsys Anti-HCV, an electrochemiluminescence (ECL) assay.

The OraQuick HCV Rapid Antibody Test is designed for use with venipuncture whole-blood samples. The test has an estimated sensitivity of at least 99%. The device uses a test strip coated with HCV antigens. After the blood sample is mixed with buffer, the test strip is placed into the test vial. The strip is read 20-40 minutes later; the appearance of a colored line indicates the detection of anti-HCV. All positive test results should be confirmed with further testing.

Assays for serum HCV RNA use signal amplification (branched DNA [bDNA]) or target amplification techniques (real-time polymerase chain reaction [RT-PCR], transcription-mediated amplification [TMA]) (see Tables 1 and 2 below).^{[1, 2, 3]}

Table 1. FDA-Approved Qualitative HCV RNA Assays (Open Table in a new window)

FDA = US Food and Drug Administration; HCV = hepatitis C virus; RT-PCR = real-time polymerase chain reaction; TMA = transcription-mediated amplification.

Table 2. FDA-Approved Quantitative HCV RNA Assays (Open Table in a new window)

bDNA = branched DNA; FDA = US Food and Drug Administration; HCV = hepatitis C virus; RT-PCR = real-time polymerase chain reaction.

HCV genotyping can be performed by means of direct sequence analysis, reverse hybridization to genotype-specific oligonucleotide probes, or restriction fragment length polymorphisms (RFLPs).

The Trugene HCV genotyping assay is based on direct sequencing followed by comparison with a reference sequence database. The Versant HCV line probe assay (formerly known as INNO LiPA HCV II) is based on reverse hybridization of a PCR amplicon on a nitrocellulose strip coated with genotype-specific oligonucleotide probes; the Roche Linear Array test uses a similar methodology.

The World Health Organization (WHO) estimates that 170 million individuals worldwide are infected with hepatitis C virus (HCV). However, the prevalence of HCV infection varies throughout the world. For example, Frank et al reported in 2000 that Egypt had the highest number of reported infections, largely attributed to the use of contaminated parenteral antischistosomal therapy.^[4] This led to a mean 22% prevalence of HCV antibodies among Egyptians.

According to the US Centers for Disease Control and Prevention (CDC), an estimated 1.8% of the US population is positive for HCV antibodies. Because 3 of 4 seropositive persons are also viremic, this percentage corresponds to an estimated 2.7 million people with active HCV infection nationwide. HCV infection accounts for 20% of all cases of acute hepatitis, an estimated 30,000 new acute infections, and 8000-10,000 deaths each year in the United States.

Medical care costs associated with the treatment of HCV infection in the United States are estimated to exceed $600 million a year. Most patients infected with HCV have chronic liver disease, which can progress to cirrhosis and hepatocellular carcinoma (HCC). Chronic infection with HCV is one of the most important causes of chronic liver disease and, according to a report by Davis et al, the most common indication for orthotopic liver transplantation (OLT) in the United States.^[5]

Guidelines from the American Association for the Study of Liver Diseases (AASLD) on the diagnosis and management of HCV infection (last updated in 2009) recommend that as part of a comprehensive health evaluation, all persons should be screened for a history of behaviors that place them at high risk for HCV infection. HCV testing should be performed routinely in individuals found to be at risk, who include the following^[1] :

• Persons who have injected illicit drugs in the recent and remote past, including those who injected only once and do not consider themselves to be drug users
• Persons with conditions associated with a high prevalence of HCV infection, including those with HIV infection, those with hemophilia who received clotting factor concentrates before 1987, those who have ever been on hemodialysis, and those with unexplained abnormal serum aminotransferase levels
• Recipients of transfusions or organ transplants before July 1992, including those who were notified that they had received blood from a donor who later tested positive for HCV infection, those who received a transfusion of blood or blood products, and those who received an organ transplant
• Children born to HCV-infected mothers
• Healthcare, emergency medical, and public safety workers who have experienced a needlestick injury or mucosal exposure to HCV-positive blood
• Current sexual partners of HCV-infected persons

The diagnosis of acute or chronic HCV infection requires testing with serologic assays for specific antibody to HCV (anti-HCV) and molecular assays for HCV RNA. Anti-HCV testing is also used to screen for infection. In the past, qualitative HCV RNA assays were preferred to quantitative assays for diagnosis because of their greater sensitivity. However, the sensitivities of the newer quantitative HCV RNA assays are comparable to those of qualitative assays, and quantitative testing is now recommended for diagnosis.^[1]

In addition to conventional serologic testing, a portable and easy-to-use assay, the OraQuick HCV Rapid Antibody Test, was approved by the US Food and Drug Administration (FDA) in June 2010. The new test provides results in 20 minutes and is indicated for HCV screening in persons who are at risk for hepatitis or show signs or symptoms of hepatitis. The test should not be used to make a final diagnosis of HCV infection.

HCV genotyping is helpful for predicting the likelihood of response and planning the duration of treatment. However, none of the commercially available tests have been approved by the FDA.

The AASLD guidelines make the following recommendations for diagnostic testing of acute and chronic HCV infection^[1] :

• Patients suspected of having acute or chronic HCV infection should first be tested for anti-HCV
• HCV RNA testing should be performed in patients with a positive anti-HCV test result; patients for whom antiviral treatment is being considered, using a sensitive quantitative assay; and patients with unexplained liver disease whose anti-HCV test yields negative results and who are immunocompromised or are suspected of having acute HCV infection
• HCV genotyping should be performed in all HCV-infected persons before interferon-based treatment to assist in planning the dosage and duration of therapy and to estimate the likelihood of response

Differentiation of acute from chronic hepatitis C virus (HCV) infection depends on the clinical presentation (eg, the presence of symptoms or jaundice or elevation of serum alanine aminotransferase [ALT] levels). HCV RNA can be detected in serum as early as 2 weeks after an acute exposure, whereas anti-HCV generally is not detectable before 8-12 weeks. The interpretation of HCV assays is outlined in Table 3.^[1]

Table 3. Interpretation of HCV Assays (Open Table in a new window)

False-negative results for anti-HCV serology can occur in immunocompromised persons, such as those with HIV type 1 infection, renal failure, or HCV-associated essential mixed cryoglobulinemia. False-positive enzyme immunoassay (EIA) results are more likely to occur in persons without risk factors and in those without signs of liver disease, such as blood donors or healthcare workers.

Serum HCV RNA levels help predict the likelihood of a response to treatment, and quantitative changes in serum HCV RNA can also be used to monitor treatment response. To avoid confusion, the same quantitative test should be used throughout therapy, and results should be reported in international units (IU) so that the data are readily comparable.

Genotyping is useful in the clinical management of HCV infection for predicting the likelihood of response and determining the optimal duration of therapy. Patients with genotypes 1 and 4 are generally treated for 12 months, whereas 6 months of treatment is sufficient for other genotypes.

In patients undergoing treatment of hepatitis C virus (HCV) infection, monitoring of HCV RNA by means of a sensitive assay, along with a complete blood cell count (CBC) and measurement of serum creatinine and alanine aminotransferase (ALT) levels, is recommended at weeks 4, 12, and 24; at 4- to 12-week intervals thereafter; at the end of treatment; and 24 weeks after treatment is stopped.^[1]