ring vaccination of their close contacts have been shown to be cost-effective (Hutton et al., 2007). That suggests that foreign-born persons from countries that have chronic HBV rates of 2% or greater should be screened for HBV infection. If they are negative for HBV seromarkers, they should be offered vaccination.

Other populations to be tested for HBV include IDUs, pregnant women, infants born to HBsAg-positive mothers, household contacts and sex partners of HBV-infected persons, men who have sex with men, and people infected with HIV. People scheduled for immunosuppressive therapy should also be tested for HBV infection because studies have clearly shown that persons who are HBsAg-positive have a risk of 20–50% of developing flares of hepatitis when undergoing cancer chemotherapy (Lok et al., 1991; Yeo and Johnson, 2006; Yeo et al., 2000). Reactivations have also been reported to occur with other types of immunosuppressives, notably anti–tumor-necrosis factor therapy for rheumatoid arthritis and inflammatory bowel disease (Esteve et al., 2004; Ostuni et al., 2003). Most flares of hepatitis in HBsAg-positive persons in this setting are asymptomatic, but icteric flares, hepatic decompensation, and death have been reported (Lok et al., 1991; Yeo et al., 2000). It has also been demonstrated that lamivudine prophylaxis can cause a substantial reduction in the incidence and severity of hepatitis flares in HBsAg-positive persons who are undergoing cancer chemotherapy (Hsu et al., 2008; Lau et al., 2002, 2003; Li et al., 2006; Rossi et al., 2001). Therefore, all persons scheduled to undergo cancer chemotherapy or immunosuppressive treatments should be screened for hepatitis B risk factors, and followup testing for HBsAg should be performed if warranted. Persons who are HBsAg-positive should be treated as recommended by established practice guidelines (Lok and McMahon, 2009).

Hepatitis C Virus Laboratory Testing Persons at risk for hepatitis C should be tested for antibodies to HCV with a licensed enzyme immunoassay (EIA), which has a high sensitivity (Alter et al., 2003). As with all screening tests, the predictive value of a positive test varies with the population prevalence, which for HCV is lowest in volunteer blood donors and highest in IDUs. False-negative EIA tests may occur in immunosuppressed populations, such as patients on hemodialysis or infected with HIV (Rahnavardi et al., 2008; Thio et al., 2000). In those settings, EIA-negative persons suspected of having HCV infection should also be tested for HCV RNA (Ghany et al., 2009). Table 5-3 provides guidance on the interpretation of hepatitis C test results.

HCV EIA-positive results should be confirmed with a second test, ideally before the information is presented to the patient to minimize the unnecessary harm of a false-positive result. There are two separate goals

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