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CAP Home > CAP Reference Resources and Publications > CAP TODAY > CAP TODAY 2005 Archive > Lab diagnosis and evaluation of treatment for HCV
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  Lab diagnosis and evaluation
  of treatment for HCV

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  cap today

April 2005
Feature Story

CAP TODAY published an article in November 2000 about Nancy Cornish, MD, Director of Microbiology, Methodist Hospital and Children’s Hospital, Omaha, who is working to improve physician test-ordering. She teaches Methodist’s physicians about lab tests through periodic clinical briefs, which she writes and distributes. The response of CAP TODAY readers to Dr. Cornish’s work was so enthusiastic and the requests for copies of her briefs so numerous that we asked her to share the clinical briefs she writes as they become available. Here, this month, is her word on hepatitis C virus infection.

Chronic hepatitis C virus infection is now a disease that can be treated. The introduction of pegylated interferons in combination with ribavirin cures HCV infection in over 50 percent of adults. Chronic infection is defined as the presence of HCV RNA in the blood for more than six months. Facts about HCV infection include the following:

  • Most common chronic bloodborne infection in the U.S.
  • Leading cause of cirrhosis in the U.S.
  • 10,000 to 20,000 deaths per year, and this number is expected to triple in the next 10 to 20 years. Compares to colon cancer at 30,000 deaths per year.
  • Associated with an increased risk of liver cancer.
  • Most common reason for liver transplant in the U.S.

Health care professionals in primary care, specialty, and public health settings should routinely question patients about risk factors for HCV infection. Routine HCV testing is recommended for the following groups:

  • Persons who ever injected illegal drugs, including those who injected once or a few times many years ago.
  • Persons who received a blood transfusion or organ transplant before July 1992.
  • Persons who received clotting factor concentrates before 1987.
  • Persons who were ever on long-term dialysis.
  • Children (after 18 months of age) born to HCV-positive women.
  • Health care, emergency medical, and public safety workers after needlesticks, sharps, or mucosal exposures to HCV-positive blood.
  • Persons with evidence of chronic liver disease.
  • HIV-positive patients.

It is estimated that the virus can remain viable on unclean surfaces for up to four days and perhaps longer. Therefore, sharing household items such as nail clippers, toothbrushes, or razors should be discouraged in family members or others who share a house with somebody with documented hepatitis C infection. Because the risk of infection is low, routine testing for hepatitis is not recommended for individuals living with an infected person or having sex with an infected steady partner. However, these individuals should be tested if they request it. Other risk factors that may lead to blood exposure and to consider when talking to patients are sex with multiple partners or prostitutes, sexual practices that lead to traumas, intranasal cocaine use, tattoos, body piercing, and manicures. However, in many patients infected with hepatitis C, the source of the infection may never be identified.

Hepatitis C virus is an RNA virus transmitted via blood. It has six major genotypes and 50 subtypes. Genotype 1 causes 70 percent to 75 percent of infections in the U.S. and is characterized by a lower rate of response to treatment (50 percent cure rate). Genotypes 2 and 3 have a much better response to treatment (80 percent cure rate). It is estimated that 85 percent of adults who are infected with hepatitis C go on to have chronic infection. Chronic infection is promoted by a high rate of viral mutation, lack of a vigorous host T-cell response, and replication in hepatocytes without cytotoxicity.

Approximately 1.8 percent of the U.S. population is infected (approximately four million people). The highest prevalence is in the 40-year to 60-year age range. Infection is usually asymptomatic; thus most people are unaware of their disease. Acute infection, though rarely recognized, has an incubation period of two to 26 weeks. Viral RNA is detected first, and shortly thereafter antibodies develop. Only 15 percent of those infected go on to spontaneously cure their disease. In practice, most people are diagnosed when routine blood tests reveal abnormal liver chemistries, they donate blood, or a physician notes risk factors and screens for the disease. Many people present for the first time with end-stage liver disease. Patients may present with extra-hepatic manifestations of chronic disease, which include rheumatoid symptoms, keratoconjunctivitis sicca, lichen planus, glom er ulo ne phri tis, lymphoma, essential mixed cryoglobulinemia, porphyria cutanea tarda, and depression.

Because testing for the presence of hepatitis C is complicated and false-positive and false-negative results occur, an algorithm for the use of laboratory tests to diagnose patients with hepatitis C has been developed by the Centers for Disease Control and Prevention. This algorithm (Related article: Reflex hepatitis C testing protocol) is designed to be cost-effective and produce accurate results. The tests available for diagnosis of hepatitis C are as follows:

HCV antibody screening test (EIA)

Advantages of this test:

  • Reproducible, inexpensive, FDA-approved for use.
  • Suitable for screening at-risk populations and those with clinical liver disease.
  • Negative results are sufficient to exclude diagnosis of chronic HCV infection in immunocompetent patients.

Disadvantages of this test:

  • Positive results of screening tests must be confirmed by more specific tests.
  • False-negatives may occur in hemodialysis and immunodeficient patients.
  • Negative results may occur in acute infections as antibodies may take up to six weeks to develop after onset of symptoms of acute hepatitis.

HCV antibody confirmation Recombinant Immuno Blot Assay, or RIBA

Advantages of this test:

  • FDA-approved for confirmatory testing of positive antibody screening test.
  • High specificity in detection of antibodies.
  • Can be performed on same serum submitted for initial antibody screening test.

Disadvantages of this test:

  • Positive result does not distinguish between past infection or chronic disease.
  • Extra test which may not be needed in patient with high likelihood of having disease.
  • Needed to confirm positive results in infected persons who have spontaneous cure of disease and those with probable false-positive results in the antibody screening assay.

HCV RNA quantitative PCR (viral load)

This test detects viral RNA. The lower limit of detection is 200 IU/mL (500 RNAcopies per mL). Results are reported as IU/mL.

Advantages of this test:

  • Can be used as supplemental test in patient suspected of having chronic disease with a positive antibody screening test.
  • Can be used for diagnosis of acute infection and in immunodeficient patients suspected of having disease with a negative antibody screen test.
  • Used to monitor therapy in patients with chronic disease.

Disadvantages of this test:

  • HCV RNA can be transiently negative in persons with acute infection but they can still go on to develop chronic infection.
  • HCV RNA can be intermittently positive in patients with chronic infection.
  • Use as supplemental test is valid only when the test is positive, that is, patient has detectable viral load.
  • Special handling of serum sample collected for testing is necessary for accurate results; if specimen is not collected or transported properly, false-negative results may be reported.
  • False-positive results can occur through contamination.

HCV genotype

This test categorizes type of viral RNA present (performed via PCR and subsequent nucleic acid sequencing).

Advantages of this test:

  • Essential test to perform once to evaluate patient before start of therapy.
  • Results determine what dose and type of medication and length of treatment will be used.
  • May help identify source of infection.
  • Assess likelihood of response to therapy.

Disadvantages of this test:

  • Results may not be obtainable in patients with low viral loads (less than 1,000 RNA copies per mL) or in cases where there are mixed genotypes causing infection.
  • Special handling of serum sample collected is necessary for accurate results; if specimen is not collected or transported properly, false-negative results may be reported.

HCV RNA qualitative PCR

This test detects viral RNA. It has a lower limit of detection of 50 IU/mL (100 RNA copies per mL). Results are reported as negative or positive for HCV RNA.

Advantages of this test:

  • Most sensitive PCR test available.
  • Used clinically at end of treatment and at end of followup, to assess treatment response.
  • Used as confirmation of initial negative quantitative PCR test.

Disadvantages of this test:

  • Special handling of serum sample collected is necessary for accurate results; if specimen is not collected or transported properly, may have false-negative results.

Other tests

Liver function tests and liver biopsies are not sensitive or specific enough to be used for screening. They may be the initial test that triggers testing for hepatitis C, and they are used as adjunct tests by specialists in treatment of hepatitis C who are caring for patients with the disease.

Flow chart

The HCV antibody screen that we offer gives us the ability to separate probable false-positive reactions from true-positive reactions by means of a signal-to-cutoff ratio.

  • Positive screens that have a low signal-to-cutoff ratio (<3.8) will be automatically reflexed to a RIBA confirmatory test before reporting the antibody screen. If the RIBA is negative, the screen will be reported, the patient will be considered not infected with hepatitis C, and the screen will be considered to be a false-positive.
  • If the RIBA is positive, which should happen rarely with a low signal-to-cutoff ratio, the physician will be called and blood obtained for a hepatitis C virus quantitative PCR and, if positive, reflex to genotype if possible and clinically appropriate.
  • If the PCR quantitative test is positive, the genotype will be done and the patient considered to have active infection with hepatitis C and recommended for evaluation by a specialist in hepatitis C disease.
  • If the PCR is negative, then the patient may be one of the 15 percent who has spontaneous cure of the disease, in which case he or she will be positive for hepatitis C antibodies but negative for active disease by the PCR results (no viral RNA detected). A comment will be in the report that a single negative PCR result does not rule out active infection, and a second PCR (qualitative test) is recommended within a month.
  • However, if the HCV antibody screen has a high signal-to-cutoff ratio (> to 3.8), this indicates the patient has a greater than 95 percent chance of truly being infected. The physician will be called and blood obtained for the supplemental tests. The supplemental test to confirm the antibody screen in this case will be a hepatitis C virus quantitative PCR.
  • If this is positive, the specimen will automatically have a genotype done and the patient will be considered to have active infection with hepatitis C and recommended for evaluation by a specialist in hepatitis C disease.
  • If the PCR quantitative is negative, the specimen will automatically be reflexed to a RIBA confirmatory test. If negative, the screen result would be reported and the patient considered not infected with hepatitis C (false-positive antibody screen). If the RIBA is positive, then the patient is positive for hepatitis C antibodies and a single negative PCR result does not rule out active infection. The recommendation is a second PCR (qualitative) in a month to confirm spontaneous cure.

Children

Infection in children is not as common as in adults, with a prevalence of 0.2 percent in children under 12 years of age and 0.4 percent in children 12 to 19 years of age. Almost half of the children infected spontaneously cure their disease. Of those chronically infected, less than 10 percent go on to have chronic hepatitis and less than five percent progress to cirrhosis.

Infants born to hepatitis C infected mothers have passively acquired maternal antibody for up to 18 months after birth and, therefore, should only be screened using an HCV antibody screening test after 18 months of age. If earlier diagnosis is required, a qualitative PCR can be performed at one to two months of age; however, a positive result doesn’t mean the child will be chronically infected and false-positive results occur.

There are no FDA-licensed therapies for children younger than 18 years of age. However, therapy may be indicated in select cases. Consultation with a pediatric specialist with experience in treating HCV infections in children is warranted.

Counseling of patients with HCV infection

All people with HCV infection should be considered infectious and informed of the possibility of transmission to others, and they should refrain from donating blood, organs, tissues, or semen. They should not share toothbrushes, nail clippers, or razors. They should be counseled to avoid hepatotoxic agents such as medications and alcohol. If they are susceptible, they should be vaccinated against hepatitis A and B viruses.

References

  1. Guidelines for laboratory testing and result reporting of antibody to hepatitis C virus. MMWR, Feb. 7, 2003, vol. 52, no. RR-3. (Free CME credit at end of report.)
  2. National Institutes of Health, Consensus Statement of Management of Hepatitis C: 2002, vol. 19, no. 3, June 10-12.
  3. American Academy of Pediatrics, Red Book, 26th ed., 2003.

Online references

  1. National Institutes of Health Web site; www.health.nih.gov . Search under hepatitis C.
  2. CDC Web site; www.cdc.gov. Search under hepatitis C. Online free CME credit can be obtained at www2a.cdc.gov/ce/availableactivities.asp. Toll-free number for additional clinical help is 1-888-4HEPCDC.
 
 

 

 

   
 
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