Pathology Associates Of Lexington, P.A.
Pathology Associates Of Lexington, P.A.
Pathology Associates Of Lexington, P.A.
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Hepatitis C tests, blood

  • Emergency HCV antibody screen: Unlike the HIV situation, there is no such test for HCV.
  • Elective HCV antibody screen: Use local EIA test for HCV antibodies (to a single recombinant protein reagent antigen...c100-3) to screen those with high risk factors (see below) and those with abnormal LFTs (if any risk factors).
    1. LML's  EIA 2nd generation, multiple-antigen test is best diagnostic screen test because less false positives
    2. 3rd gen. more sensitive but less specific (more false positives) and more ideal for screening donor blood units
  • HCV antibody supplemental test: tests by RIBA (recombinant immunoblot assay, originally a supplemental...not confirmatory...test) apply patient's antibody-containing serum to bands of 4 HCV proteins in a strip...might use it when a surprise EIA screen positive in a low risk patient. "Positive" is reactivity to 2 or more antigens & some feel this 2nd gen. (RIBA-2 SIA) test is confirmatory when reactive to >2 antigens.
  • HCV confirmatory test:  
    • prior to the RNA tests, the Western Blot test (denatured HCV is antigen reagent)...detecting circulating HCV antibody in our most specific (least false positive rate) fashion at the time...was the confirmatory lab diagnostic test.
    • HCV RNA detection (quant): If EIA test positive, get HCV RNA by PCR or TMA or b-DNA quantitative (sensitive to as low as 550-600 IU/mL)...if it is negative,
    • HCV RNA detection (qual): If EIA test negative, get HCV RNA by TMA or PCR qualitative (sensitive to as low as 10-100 IU/mL)...if it is negative,
    • see RIBA, above.
  • "Indeterminate" test results: this problem has to be addressed with retesting or serial testing, alternate testing, clinicopathological correlation, etc.
  • Reference Labs: we use LML for EIA and Quest or Specialty Lab for TMA, PCR, and b-DNA. Here is a decision CHART with reference lab flow chart links.
  • Discordant test results: Is this an HCV-positive patient or not!? One can end up with a mix of positive and negative results depending on whether you are comparing tests for antibodies vs.  tests for circulating HCV RNA. And, there can be differences in sensitivity and false positive rates between types of antibody tests, types of HCV protein tests and types of HCV RNA tests. Keep in mind that: (1) all tests have false positives, (b) some HCV-infected patients cannot (or have not yet) mounted a detectible antibody response, and (c) some HCV-infected patients flux in and out of periods of viremia (RNA detectibility). Up to 15% of chronically HCV-infected individuals followed over time will have periods of viral RNA antigen "drop out" (negativity for RNA detectibility).
The Veterans Administration guidelines for those at risk are:
    • Vietnam-era veteran
    • Blood transfusion before 1992
    • Past or present intravenous drug use
    • Unequivocal blood exposure of skin or mucous membranes
    • History of multiple sexual partners
    • History of hemodialysis
    • Tattoo or repeated body piercing
    • History of intranasal cocaine use
    • Unexplained liver disease
    • Unexplained/abnormal ALT (SGPT)
    • Intemperate or immoderate use of
      alcohol
As currently determined by dates of service or in the age range of 40 to 55 years
Defined as more than 10 lifetime sexual partners
Defined as more than 50g of alcohol per day for ten or more years (roughly 10-14g of alcohol = 1 beer)
Note:
These variables may be interrelated and are not necessarily independently related to risk for HCV infection.

References:

  1. CAP TODAY 16(4), April 2002.
  2. Urdea MS, [of Chiron Corp.] "Hepatitis C-diagnosis and monitoring", Clinical Chemistry 43(8):1507-1511, 1997.

 

(posted May 2002; latest addition, 25 July 2012)

 
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