Putting Prevention into Practice
An Evidence-Based Approach
Screening for Hepatitis C in Adults
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Am Fam Physician. 2005 Mar 1;71(5):955-956.
This clinical content conforms to AAFP criteria for evidence-based continuing medical education (EB CME). EB CME is clinical content presented with practice recommendations supported by evidence that has been systematically reviewed by an AAFP-approved source. The practice recommendations in this activity are available at http://www.ahrq.gov/clinic/uspstf/uspshepc.htm.
DV, a 35-year-old woman, is concerned about hepatitis C virus (HCV) infection after reading about celebrities who have the infection. She has been in a monogamous relationship for 10 years, has never used illicit drugs, and has never received a blood transfusion. She has no symptoms and is healthy.
Case Study Questions
Based on the U.S. Preventive Services Task Force (USPSTF) recommendations on HCV screening, which of the following statements are correct?
A. She is at increased risk for HCV infection.
B. She is not at increased risk for HCV infection.
C. She should be screened for HCV infection.
D. She should not be screened for HCV infection.
Which of the following statements about HCV epidemiology are correct?
A. Intravenous drug use is a risk factor for HCV infection.
B. Receiving a blood transfusion before 1990 is a risk factor for HCV infection.
C. Most persons infected with HCV will develop liver cirrhosis.
D. HCV is the most common bloodborne pathogen in the United States.
DV reveals that she actually came to your office to confirm a positive test result from a walk-in laboratory testing center. She shows you her laboratory report with a positive test for anti-HCV antibodies. What is the most appropriate next step?
A. Repeat the enzyme immunoassay.
B. Initiate antiviral therapy.
C. Order a liver biopsy.
D. Order an HCV strip recombinant immunoblot assay.
E. Immunize her against hepatitis A and hepatitis B.
1.The correct answers are B and D. There is no need to screen DV for HCV infection because she has no risk factors. The USPSTF recommends against routine screening for HCV infection in asymptomatic adults who are not at increased risk for infection. The prevalence of HCV infection in the general population is low (about 2 percent). A minority of HCV-infected persons develop major negative health outcomes such as cirrhosis, and no treatment has a proven beneficial effect on long-term health outcomes. Also, treatment has frequent adverse effects, and some patients will withdraw from therapy because of these effects.
Even if proven treatments were available, the potential benefits of general population screening would be small. For example, with such a low disease prevalence, positive results from even a highly specific test, such as the enzyme immunoassay (EIA), which has 97 percent specificity, will generate a nearly 60 percent false-positive rate. This could lead to unnecessary work-ups, including liver biopsies, and psychologic harms, such as labeling. Therefore, the USPSTF concludes that the potential harms of general population screening are likely to exceed the benefits.
2.The correct answers are A, B, and D. HCV infection is the most common bloodborne pathogen in the United States and is associated with about 10,000 deaths annually. The National Hepatitis Screening Survey found that intravenous drug use was the strongest risk factor for HCV infection, followed by hemodialysis, sex with an intravenous drug user, a history of blood transfusion before 1990, and male gender. HCV is acquired primarily by large or repeated percutaneous exposure to blood. Estimates of the prevalence of HCV infection in intravenous drug users vary from 50 to 90 percent.
The natural course of chronic HCV infection varies widely. Most people with chronic HCV infection never develop the disease or have only mild liver disease. Available evidence indicates that only 10 to 20 percent of persons with chronic HCV infection develop cirrhosis after 20 to 30 years. There is inadequate evidence that antiviral therapy is effective in decreasing morbidity and mortality from chronic liver disease. Thus, the USPSTF concludes that the evidence is insufficient to recommend for or against routine screening for HCV infection in adults at increased risk.
3.The correct answer is D. As stated above, a positive EIA result in a low-prevalence population is more likely to be false positive, hence it should be confirmed with another test. The strip recombinant immunoblot assay is a commonly used confirmatory test. Patients with positive results on both tests are considered to have confirmed evidence of HCV exposure, although they may not have active infection. Polymerase chain reaction (PCR) testing is considered the gold standard for detecting active HCV infection. Some experts prefer PCR as the confirmatory test. Given DV’s low risk, there is a good likelihood that her EIA results are false positive.
Because antibody-based screening tests for HCV do not discriminate between persistent and resolved infection, further work-up to determine the need for antiviral therapy often includes PCR testing for viremia, checking transaminase levels, and performing a liver biopsy. Only a minority of patients referred for treatment of HCV infection were eligible for and received treatment. Patient withdrawal from antiviral treatment because of adverse effects varies from 5 to 20 percent. The most common adverse event is an influenza-like syndrome, including myalgia, fatigue, headache, and fever. Although antiviral therapy frequently leads to sustained reduction in viremia, the long-term health benefit of this therapy (e.g., preventing or decreasing progression to liver cirrhosis) has yet to be established. The benefits of other interventions in HCV-infected patients, including immunization against hepatitis A and B and counseling to reduce liver damage from alcoholism, are not well established.
Chou R. Screening for hepatitis C virus infection: systematic evidence review no. 24. Prepared by the Oregon Evidence-based Practice Center, Oregon Health & Science University under contract no. 290–97–0018. Rockville, Md.: Agency for Healthcare Research and Quality, 2004.
Chou R, Clark EC, Helfand MH. Screening for hepatitis C virus infection: a review of the evidence for the U.S. Preventive Services Task Force. Ann Intern Med. 2004;140:465–79.
U.S. Preventive Services Task Force. Screening for hepatitis C in adults: recommendation statement. Ann Intern Med. 2004;140:462–4.
The case study and answers to the following questions on screening for hepatitis C in adults are based on the recommendations of the U.S. Preventive Services Task Force (USPSTF), part of the Put Prevention into Practice program of the Agency for Healthcare Research and Quality (AHRQ). This recommendation was released in 2004. More detailed information on this subject is available in the USPSTF Recommendations and Rationale, the summary of the evidence, and the systematic evidence review on the USPSTF Web site (http://www.ahrq.gov/clinic/uspstfix.htm). The summary of the evidence and recommendation statement are available in print by subscription through the AHRQ Publications Clearinghouse (800–358–9295, e-mail, email@example.com).
This case study is part of AFP’s CME. See “Clinical Quiz” on page 847.
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