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
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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)
Design Features
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)
Assay |
Method |
Lower Limit of Detection (IU/mL) |
COBAS Amplicor HCV Test (v2.0) |
Manual RT-PCR |
50 |
COBAS Ampliprep/COBAS Amplicor HCV Test (v2.0) |
Semiautomated RT-PCR |
50 |
COBAS Ampliscreen HCV Test (v2.0) |
Semiautomated RT-PCR |
< 10 |
Versant HCV RNA Qualitative Assay |
Semiautomated TMA |
50 |
PROCLEIX HIV-1/HCV Assay |
Manual TMA |
< 50 |
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)
Assay |
Method |
Sensitivity (IU/mL) |
Dynamic Range (IU/mL) |
Versant HCV RNA 3.0 Assay (bDNA) |
Signal amplification (bDNA) |
615 |
615 to 7.7 × 106 |
COBAS Ampliprep/COBAS TaqMan HCV Test |
Fully automated RT-PCR |
15 |
43 to 6.9 × 107 |
COBAS TaqMan HCV Test v2.0 for use with High Pure System |
Semiautomated RT-PCR |
25 |
25 to 3 × 108 |
Abbott RealTime HCV |
Semiautomated RT-PCR |
12 |
12 to 1 × 108 |
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 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
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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
Clinical Implementation
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)
Anti-HCV |
HCV RNA |
Interpretation |
Positive |
Positive |
Acute or chronic HCV, depending on clinical context |
Positive |
Negative |
Resolution of HCV; acute HCV during period of low-level viremia |
Negative |
Positive |
Early acute HCV infection; chronic HCV in setting of immunosuppressed state; false-positive HCV RNA test result |
Negative |
Negative |
Absence of HCV infection |
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.
References
1.
Ghany MG, Strader
DB, Thomas DL, Seeff
LB. Diagnosis,
management, and
treatment of
hepatitis C: an
update. Hepatology.
Apr
2009;49(4):1335-74.
[Medline].
[Full Text].
2.
Pittaluga F, Allice
T, Abate ML, et al.
Clinical evaluation
of the COBAS
Ampliprep/COBAS
TaqMan for HCV RNA
quantitation in
comparison with the
branched-DNA assay.
J Med Virol. Feb
2008;80(2):254-60.
[Medline].
3.
Vermehren J, Kau A,
Gartner BC, Gobel R,
Zeuzem S, Sarrazin
C. Differences
between two
real-time PCR-based
hepatitis C virus
(HCV) assays (RealTime
HCV and Cobas
AmpliPrep/Cobas
TaqMan) and one
signal amplification
assay (Versant HCV
RNA 3.0) for RNA
detection and
quantification. J
Clin Microbiol. Dec
2008;46(12):3880-91.
[Medline].
[Full Text].
4.
Frank C, Mohamed MK,
Strickland GT,
Lavanchy D, Arthur
RR, Magder LS. The
role of parenteral
antischistosomal
therapy in the
spread of hepatitis
C virus in Egypt.
Lancet. Mar 11
2000;355(9207):887-91.
[Medline]
5.
Davis GL, Balart LA,
Schiff ER, et al.
Treatment of chronic
hepatitis C with
recombinant
interferon alfa. A
multicenter
randomized,
controlled trial.
Hepatitis
Interventional
Therapy Group. N
Engl J Med. Nov 30
1989;321(22):1501-6.
[Medline].
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