Hepatitis C Virus Antibody Screen for Cadaveric or Hemolyzed Specimens, Serum
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Hepatitis C virus (HCV) is recognized as the cause of most cases of post-transfusion hepatitis and is a significant cause of morbidity and mortality worldwide. In the United States, HCV infection is quite common, with an estimated 3.5 to 4 million chronic HCV carriers.
HCV antibodies are usually not detectable during the early months following infection, but they are almost always detectable by the late convalescent stage (>6 months after onset of acute infection). These antibodies do not neutralize the virus, and they do not provide immunity against this viral infection. Loss of HCV antibodies may occur many years following resolution of infection.
Despite the value of serologic tests to screen for HCV infection, several limitations of serologic testing are known:
-There may be a long delay (up to 6 months) between exposure to the virus and the development of detectable antibodies.
-False-reactive screening test results can occur.
-A reactive screening test result does not distinguish between past (resolved) and present HCV infection.
-Serologic tests cannot provide information on clinical response to antiviral therapy.
Positive screening serologic test results should be followed by a confirmatory or supplemental test, such as recombinant immunoblot assay (RIBA) for HCV antibodies or nucleic acid test for HCV RNA. Although nucleic acid tests provide a very sensitive and specific approach to directly detect HCV RNA in a patient's blood, they are not suitable for use in testing cadaveric or hemolyzed serum specimens due to interference of heme with the nucleic acid amplification processes.
Screening cadaveric or hemolyzed serum specimens for hepatitis C virus-specific antibodies
Note: This test is not intended for screening blood, cell, or tissue donors.
All specimens with reactive screening test results and signal-to-cutoff ratios of > or =1.0 will be reflexed to the hepatitis C virus (HCV) antibody confirmatory test by recombinant immunoblot assay (RIBA) at an additional charge. Additional testing is needed to differentiate between past (resolved) and chronic hepatitis C.
A negative screening test result does not exclude the possibility of exposure to or infection with HCV. Negative screening test results in individuals with prior exposure to HCV may be due to antibody levels below the limit of detection of this assay or lack of reactivity to the HCV antigens used in this assay. Patients with recent HCV infections (<3 months from time of exposure) may have false-negative HCV antibody results due to the time needed for seroconversion (average of 8 to 9 weeks).
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Infants born to hepatitis C virus (HCV)-infected mothers may have false-reactive HCV antibody screening test results and false-positive HCV antibody confirmatory test results, due to transplacental passage of maternal HCV-specific IgG antibodies). HCV antibody testing is not recommended until at least 18 months of age in these infants.
Not useful for ruling out acute HCV infection.
Not useful for differentiation between resolved and acute or chronic hepatitis C infection.
Performance characteristics of the EIA have not been established for the following types of serum specimen:
-Grossly hemolyzed (hemoglobin level of >800 mg/dL). Hemolyzed specimens with hemoglobin level of < or =800 mg/dL will be accepted and tested.
-Grossly icteric (total bilirubin level of >30 mg/dL). Icteric specimens with total bilirubin levels < or =30 mg/dL will be accepted and tested.
-Grossly lipemic (triglyceride level of >3,000 mg/dL). Lipemic specimens with a triglyceride level of < or =3,000 mg/dL will be accepted and tested.
-Presence of particulate matter
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
Clinical References Provides recommendations for further in-depth reading of a clinical nature
1. Carithers RL, Marquardt A, Gretch DR: Diagnostic testing for hepatitis C. Semin Liver Dis 2000;20(2):159-171
2. Alter MJ, Kuhnert WL, Finelli L: Centers for Disease Control and Prevention: Guidelines for laboratory testing and result reporting of antibody to hepatitis C virus. MMWR Morb Mortal Wkly Rep 2003;52(No. RR-3):1-14
3. Pawlotsky JM: Use and interpretation of virological tests for hepatitis C. Hepatology 2002;36:S65-S73