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Table 1 Comparison of diagnostic laboratory tests used to detect exposure and activity of HCV infection

From: Hepatitis virus (HCV) diagnosis and access to treatment in a UK cohort

Screening tool HCV-Ab HCV-Ag PCR for HCV RNA
Benefits ♦ Widely available;
♦ Inexpensive;
♦ Much experience and data for use as first-line approach to screening for HCV exposure (underpins many old seroprevalence studies).
♦ Diagnostic of active infection (not past exposure);
♦ Improved specificity and reduced window period compared to HCV-Ab [14, 29, 42,43,44,45].
♦ Accepted gold-standard diagnostic test for active infection (not past exposure);
♦ Allows quantitative monitoring of viraemia; useful for monitoring therapy;
♦ Genome amplification allows other information to be ascertained (e.g. genotype; drug resistance);
♦ Can potentially be applied to dried blood spots (DBS).
Challenges ♦ Subject to inter-assay variability and a variable rate of false positive results [46, 47]; false positive has been associated with ethnicity [48, 49], age [48], raised IgM and erythrocyte sedimentation rate (ESR) [46], auto-antibodies [50], and prosthetic devices [51];
♦ Test of exposure, not of active infection, so should be followed up with a more specific diagnostic test.
♦ Not universally available;
♦ More expensive than HCV-Ab;
♦ Not consistently regarded as sufficiently sensitive to replace PCR.
♦ Not universally available;
♦ Expensive: beyond the financial reach of many resource-limited settings.