Hepatitis C laboratory tests: Difference between revisions

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== Diagnosis ==
{{Hepatitis C}}
{{CMG}} ; '''Associate Editor(s)-In-Chief:''' {{JA}}
==Overview==
The laboratory diagnosis of hepatitis C infection is first made by documenting positive [[serology|serologies]] (anti-HCV antibodies), followed by HCV RNA quantification by PCR or NAT to determine the viral load and to differentiate chronic infection from remission.


The diagnosis of "hepatitis C" is rarely made during the acute phase of the disease because the majority of people infected experience no symptoms during this phase of the disease. Those who ''do'' experience acute phase symptoms are rarely ill enough to seek medical attention. The diagnosis of chronic phase hepatitis C is also challenging due to the absence or lack of specificity of symptoms until advanced liver disease develops, which may not occur until decades into the disease.
==Serologies and HCV RNA==
The diagnosis of HCV is rarely made during the acute phase given that the majority of individuals infected are asymptomatic during this phase of the disease. Chronic hepatitis C may be suspected on the basis of the [[medical history]] (particularly if there is the history of [[intravenous|IV]] or intranasal drug use), a history of piercings or [[tattoo]]s, unexplained symptoms, or abnormal levels of [[liver function test]]s found during routine blood testing.


Chronic hepatitis C may be suspected on the basis of the [[medical history]] (particularly if there is any history of IV drug abuse or inhaled substance usage such as cocaine), a history of piercings or [[tattoo]]s, unexplained symptoms, or abnormal liver enzymes or liver function tests found during routine blood testing. Occasionally, hepatitis C is diagnosed as a result of targeted screening such as [[blood donation]] (blood donors are screened for numerous blood-borne diseases including hepatitis C) or [[contact tracing]].
Hepatitis C testing begins with [[serology|serological]] blood tests used to detect antibodies against HCV in the majority of cases. Overall, anti-HCV antibody tests have a strong [[positive predictive value]] for exposure to the hepatitis C virus, but may miss patients who have not yet had [[seroconversion]].<ref name="aasld2014">AASLD/IDSA/IAS–USA. Recommendations for testing, managing, and treating hepatitis C. http://www.hcvguidelines.org. Accessed July 27, 2014.</ref><ref name="pmid29703790">{{cite journal |vauthors=Cacoub P, Desbois AC, Comarmond C, Saadoun D |title=Impact of sustained virological response on the extrahepatic manifestations of chronic hepatitis C: a meta-analysis |journal=Gut |volume=67 |issue=11 |pages=2025–2034 |date=November 2018 |pmid=29703790 |doi=10.1136/gutjnl-2018-316234 |url=}}</ref> As anti-HCV antibodies indicate exposure to the virus, but cannot determine active infection, all patients with positive anti-HCV antibody tests must undergo HCV RNA quantification by nucleic acid amplification (NAT) via [[polymerase chain reaction]] (PCR) to determine the viral load. The HCV viral load is an important factor in determining active disease and the probability of response to therapy. It is not associated with disease severity or the likelihood of disease progression.


Hepatitis C testing begins with [[serology|serological]] blood tests used to detect antibodies to HCV. Anti-HCV antibodies can be detected in 80% of patients within 15 weeks after exposure, in >90% within 5 months after exposure, and in >97% by 6 months after exposure. Overall, HCV antibody tests have a strong [[positive predictive value]] for exposure to the hepatitis C virus, but may miss patients who have not yet developed antibodies ([[seroconversion]]), or have an insufficient level of antibodies to detect. While uncommon, a small minority of people infected with HCV never develop antibodies to the virus and therefore, never test positive using HCV antibody screening.
Rarely, HCV RNA quantification is performed without prior anti-HCV antibody testing. This is only indicated in patients who have a known past history of cleared HCV infection with previous [[seroconversion]] and in [[immunocompromised]] patients.


Anti-HCV antibodies indicate exposure to the virus, but ''cannot'' determine if ongoing infection is present. All persons with positive anti-HCV antibody tests must undergo additional testing for the presence of the hepatitis C virus itself to determine whether current infection is present. The presence of the virus is tested for using molecular nucleic acid testing methods such as polymerase chain reaction (PCR), transcription mediated amplification (TMA), or branched DNA (b-DNA). All HCV nucleic acid molecular tests have the capacity to detect not only whether the virus is present, but also to measure the amount of virus present in the blood (the HCV viral load). The HCV viral load is an important factor in determining the probability of response to interferon-based therapy, but does ''not'' indicate disease severity nor the likelihood of disease progression.
Among individuals with confirmed HCV infection, genotype testing is recommended. HCV genotype testing is used tailor therapeutic regimen.<ref name="who">World Health Organization (WHO) 2014. Guidelines for the screening, care and treatment of persons with hepatitis C infection.http://www.who.int/hiv/pub/hepatitis/hepatitis-c-guidelines/en/. Accessed online on July 24,2014.</ref>
 
In people with confirmed HCV infection, genotype testing is generally recommended. There are six major genotypes of the hepatitis C virus, which are indicated numerically (e.g., genotype 1, genotype 2, etc.). HCV genotype testing is used to determine the required length and potential response to interferon-based therapy.
 
=== Laboratory Diagnosis ===


===Laboratory Tests===
* '''HCV Enzyme-linked immunosorbent assay (ELISA)'''
* '''HCV Enzyme-linked immunosorbent assay (ELISA)'''
*:* Positive within 4-10 weeks after infection
*:* Positive within 4-10 weeks after infection
*:* False negatives can occur with HIV infection, chronic renal failure, cryos
*:* False negatives can occur with [[HIV]] infection, [[chronic renal failure]], and [[cryoglobulinemia]]
* '''HCV RNA'''
* '''HCV RNA'''
*:* Polymerase chain reaction (PCR) highly sensitive for confirming viremia
*:* PCR highly sensitive for confirming viremia
*:* Predicts response to therapy but not risk of progression
*:* Predicts response to therapy but not risk of progression


There are several blood tests that can be done to determine if you have been infected with HCV. Your doctor may order just one or a combination of these tests. The following are the types of tests your doctor may order and the purpose for each:
A single positive PCR test indicates infection with HCV. Negative tests usually do not require re-testing, except in cases with high clinical suspicion.
 
''a) Anti-HCV (antibody to HCV)''
 
EIA (enzyme immunoassay) or CIA (enhanced chemiluminescence immunoassay)
Test is usually done first. If positive, it should be confirmed
RIBA (recombinant immunoblot assay)
A supplemental test used to confirm a positive EIA test
Anti-HCV does not tell whether the infection is new (acute), chronic (long-term) or is no longer present.
''b) Qualitative tests to detect presence or absence of virus (HCV RNA)''
''c) Quantitative tests to detect amount (titer) of virus (HCV RNA)''


A single positive PCR test indicates infection with HCV. A single negative test does not prove that a person is not infected. Virus may be present in the blood and just not found by PCR. Also, a person infected in the past who has recovered may have a negative test. When hepatitis C is suspected and PCR is negative, PCR should be repeated.
[[File:HCV infection diagnosis.JPG|900px|center|thumb|Source: https://www.cdc.gov/]]
 
[[File:HCV infection diagnosis.JPG]]
<br clear="left"/>
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==Follow-up testing for health care personnel exposed to HCV-positive blood==
==Follow-up Testing for Healthcare Personnel Exposed to HCV-positive Blood==
*For the source, perform baseline testing for anti-HCV.
*For the source, perform baseline serological testing using anti-HCV antibodies.
*For the person exposed to an HCV-positive source, perform baseline and follow-up testing, including
*For the person exposed to an HCV-positive source, perform baseline and follow-up testing, including
**baseline testing for anti-HCV and ALT activity AND
**baseline testing for anti-HCV and ALT activity, ''and''
**follow-up testing for anti-HCV (e.g., at 4–6 months) and ALT activity. If earlier diagnosis of HCV infection is desired, testing for HCV RNA may be performed at 4–6 weeks.
**follow-up testing for anti-HCV and ALT activity at approximately 4–6 months after exposure. If earlier diagnosis of HCV infection is desired, testing for HCV RNA may be performed at 4–6 weeks after exposure
*Confirmation by supplemental anti-HCV testing of all anti-HCV results reported as positive by enzyme immunoassay.
*Confirmation by supplemental HCV RNA testing for all positive anti-HCV results


==References==
==References==
{{Reflist|2}}
{{Reflist|2}}


[[Category:Hepatitis|C]]
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Latest revision as of 23:13, 12 June 2021

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] ; Associate Editor(s)-In-Chief: Javaria Anwer M.D.[2]

Overview

The laboratory diagnosis of hepatitis C infection is first made by documenting positive serologies (anti-HCV antibodies), followed by HCV RNA quantification by PCR or NAT to determine the viral load and to differentiate chronic infection from remission.

Serologies and HCV RNA

The diagnosis of HCV is rarely made during the acute phase given that the majority of individuals infected are asymptomatic during this phase of the disease. Chronic hepatitis C may be suspected on the basis of the medical history (particularly if there is the history of IV or intranasal drug use), a history of piercings or tattoos, unexplained symptoms, or abnormal levels of liver function tests found during routine blood testing.

Hepatitis C testing begins with serological blood tests used to detect antibodies against HCV in the majority of cases. Overall, anti-HCV antibody tests have a strong positive predictive value for exposure to the hepatitis C virus, but may miss patients who have not yet had seroconversion.[1][2] As anti-HCV antibodies indicate exposure to the virus, but cannot determine active infection, all patients with positive anti-HCV antibody tests must undergo HCV RNA quantification by nucleic acid amplification (NAT) via polymerase chain reaction (PCR) to determine the viral load. The HCV viral load is an important factor in determining active disease and the probability of response to therapy. It is not associated with disease severity or the likelihood of disease progression.

Rarely, HCV RNA quantification is performed without prior anti-HCV antibody testing. This is only indicated in patients who have a known past history of cleared HCV infection with previous seroconversion and in immunocompromised patients.

Among individuals with confirmed HCV infection, genotype testing is recommended. HCV genotype testing is used tailor therapeutic regimen.[3]

Laboratory Tests

  • HCV Enzyme-linked immunosorbent assay (ELISA)
  • HCV RNA
    • PCR highly sensitive for confirming viremia
    • Predicts response to therapy but not risk of progression

A single positive PCR test indicates infection with HCV. Negative tests usually do not require re-testing, except in cases with high clinical suspicion.

Source: https://www.cdc.gov/


Follow-up Testing for Healthcare Personnel Exposed to HCV-positive Blood

  • For the source, perform baseline serological testing using anti-HCV antibodies.
  • For the person exposed to an HCV-positive source, perform baseline and follow-up testing, including
    • baseline testing for anti-HCV and ALT activity, and
    • follow-up testing for anti-HCV and ALT activity at approximately 4–6 months after exposure. If earlier diagnosis of HCV infection is desired, testing for HCV RNA may be performed at 4–6 weeks after exposure
  • Confirmation by supplemental HCV RNA testing for all positive anti-HCV results

References

  1. AASLD/IDSA/IAS–USA. Recommendations for testing, managing, and treating hepatitis C. http://www.hcvguidelines.org. Accessed July 27, 2014.
  2. Cacoub P, Desbois AC, Comarmond C, Saadoun D (November 2018). "Impact of sustained virological response on the extrahepatic manifestations of chronic hepatitis C: a meta-analysis". Gut. 67 (11): 2025–2034. doi:10.1136/gutjnl-2018-316234. PMID 29703790.
  3. World Health Organization (WHO) 2014. Guidelines for the screening, care and treatment of persons with hepatitis C infection.http://www.who.int/hiv/pub/hepatitis/hepatitis-c-guidelines/en/. Accessed online on July 24,2014.

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