Test/type		Application	Comments
Anti-HCV
EIA, RIBA		Indicates past or present infection but does not differentiate between acute, chronic or resolved infection.	Sensitivity: ≥ 97%
			EIA alone has low positive predictive value in low-prevalence populations
		All positive EIA results should be verified with a supplemental assay (RIBA)
HCV RNA
Qualitative tests*†
	RT-PCR amplification of HCV RNA by in-house or commercial assays (e.g., Amplicor HCV)	Detects presence of circulating HCV RNA Monitors patients on antiviral therapy	Detects virus as early as 1 to 2 weeks after exposure Detection of HCV RNA during course of infection may be intermittent; a single negative RT-PCR test is not conclusive False-positive and false-negative results are possible
Quantitative tests*†
	RT-PCR amplification of HCV RNA by in-house or commercial assays (e.g., Amplicor HCV Monitor) bDNA assays (e.g., Quantiplex HCV RNA Assay)	Determines concentration of HVC RNA	Less sensitive than qualitative RT-PCR
		May be useful for assessing the likelihood of response to antiviral therapy	Should not be used to exclude the diagnosis of HCV infection or to determine treatment end point
Genotype*†
	Several methodologies available (e.g., hybridization, sequencing)	Groups isolates of HCV based on genetic differences into six genotypes and > 90 subtypes With new therapies, length of treatment may vary based on genotype	Genotype 1 (subtypes 1a and 1b) is the most common in the United States and is associated with lower response to antiviral therapy
Serotype*
	EIA based on immunoreactivity to synthetic peptides (e.g., Murex HCV Serotyping 1–6 Assay)	No clinical utility	Cannot distinguish between subtypes
			Dual infections often observed