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Laboratory Testing for Hepatitis C



Comparison of PCR, TMA, and bDNA

Slide 10

April 2008

The CDC has issued recommendations to laboratories on how to report and test subsequently to confirm the pres of Hepatitis C infection. This is a figure taken from that publication which appeared in the Morbidity and Mortality Weekly Report in 2003.

This algorithm illustrates that one should begin with screening test for anti-Hepatitis C Total Antibody. At Mayo Medical Laboratories, the test name is Hepatitis C Virus Antibody (Anti-HCV), in serum, by the chemiluminescence immunoassay. If the result is negative, then it’s reported out to the provider. If the test is positive, then laboratories and providers have the choice of either determining subsequent testing based on the signal-to-cutoff ratio or by testing all positive regardless of the signal-to-cutoff ratio, to reflex to one of two confirmatory tests.

In selection 2, one can choose an automatic reflex to confirmation of HCV Antibody by RIBA, or by choosing selection 3, with automatic reflex to reverse transcription PCR which is a molecular test to confirm the presence of HCV RNA.

One can also request Anti-HCV Confirmation (selection 4) alone after a screening test is positive, if an automatic reflex test was a not an issue. One can also request HCV RNA Detection and Quantification by RT-PCR (selection 5) here at Mayo Medical Laboratories if the HCV Anitbody reflex testing was not requested initially.

Note that with the recombinant immunoblot assay being positive, one cannot distinguish between past infections versus chronic Hepatitis C. With a positive screening test and a positive confirmation test by radio immunoblot assay, it is still necessary to do the nucleic acid test to determine if there is chronic Hepatitis C which is indicated by the presence of HCV RNA. In our Mayo Medical Laboratories practice, it is our preference to reflex after a positive HCV Antibody to the RT-PCR test since a positive HCV RNA is sufficient to confirm the presence of chronic or acute Hepatitis C without need to confirm HCV Anitbody by RIBA.

Comparison of PCR, TMA, and bDNA

 


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