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Structured Abstract
Objectives
Many patients with chronic hepatitis C virus (HCV) infection are unaware of their status. Screening could identify patients at earlier stages of disease, when interventions might be effective in improving clinical outcomes or reducing transmission risk. The purpose of this report is to systematically review the evidence on screening for HCV infection in asymptomatic adults without known liver enzyme abnormalities, including pregnant women. This review focuses on research gaps identified in the 2004 United States Preventive Services Task Force (USPSTF) review and new studies published since that review, and it reviews evidence on prenatal HCV screening not included in the 2004 USPSTF review. This report examines both direct evidence on the effects of screening for HCV infection compared to no screening on clinical outcomes, as well as the indirect chain of evidence (diagnosis, workup, and treatment) needed to understand effects of screening on clinical outcomes. Treatments evaluated included immunizations, counseling, and interventions to potentially reduce risk of mother-to-child transmission. To complement this review of screening for HCV, the Agency for Healthcare Research and Quality (AHRQ) commissioned a separate review on effectiveness of antiviral treatments.
Data sources
Articles were identified from searches (from 1947 to May 2012) of the Cochrane Database of Systematic Reviews, the Cochrane Central Register of Controlled Trials, EBM Reviews, and Ovid MEDLINE®. The searches were supplemented by reviewing reference lists and searching clinical trial registries.
Review methods
We used predefined criteria to determine study eligibility. We selected randomized trials and observational studies that evaluated effects of screening, counseling interventions, and immunizations on clinical and intermediate outcomes. We also selected studies that evaluated effects of labor and delivery practices and breastfeeding on mother-to-child transmission of HCV infection. We selected studies that evaluated the diagnostic accuracy of noninvasive tests compared to liver biopsy for diagnosing fibrosis or cirrhosis in patients with chronic HCV infection. The quality of included studies was assessed, data were extracted, and results were summarized.
Results
Of the 10,786 citations identified at the title and abstract level, we screened and reviewed 808 full-length articles. A total of 182 studies were included. There was no direct evidence on clinical benefits associated with screening compared with no screening (or comparing different screening approaches) in nonpregnant or pregnant adults. Retrospective studies found that screening strategies targeting multiple risk factors were associated with sensitivities of over 90 percent and numbers needed to screen to identify one case of HCV infection of less than 20. Narrowly targeted screening strategies based on history of intravenous drug use were associated with numbers needed to screen of less than two, but missed up to two-thirds of infected people. Data on harms of screening (such as labeling and anxiety) were sparse. Compared with liver biopsy, a number of indices based on panels of blood tests were associated with a median area under the receiver operating characteristic curve (AUROC) of 0.75 to 0.86 for diagnosing fibrosis and a median AUROC of 0.80 to 0.91 for diagnosing cirrhosis, but there was insufficient evidence to determine clinical outcomes associated with strategies incorporating noninvasive tests for evaluating patients with HCV infection. Limited evidence suggested that knowledge of HCV status and counseling interventions may reduce alcohol use and risky injection drug use behaviors, but more evidence is needed to demonstrate long-term sustainability and to understand effects on clinical outcomes and transmission risk. In pregnant women, cohort studies found no clear association between mode of delivery and risk of vertical transmission of HCV infection and consistently found no association between breastfeeding and transmission risk. Evidence on the association between other labor and delivery management practices and risk of vertical transmission of HCV infection was sparse, but suggested that prolonged rupture of membranes is associated with increased risk.
Conclusions
Although screening tests can accurately identify adults with chronic HCV infection, targeted screening strategies based on the presence of risk factors miss some patients with HCV infection. As a result, more research is needed to understand the effects of different screening strategies on clinical outcomes. Evidence on effects of knowledge of HCV status and counseling and immunizations on clinical and intermediate outcomes in patients diagnosed with HCV infection remains sparse and more research is needed to understand effective interventions for preventing vertical transmission. A complete assessment of benefits and harms of screening requires consideration of the effectiveness of antiviral regimens, which are the subject of a complementary review.
