title: Evaluation of the core antigen assay as a second-line supplemental test for diagnosis of active hepatitis C virus infection.
abstract: The British Columbia Center for Disease Control laboratory performs approximately 95% of all hepatitis C virus (HCV) antibody tests for the province's 4 million inhabitants. In 2002, the laboratory tested 96,000 specimens for anti-HCV antibodies, of which 4,800 (5%) were seroreactive and required confirmation of active infection. Although HCV RNA assays with a sensitivity of 50 IU/ml or less are recommended for the confirmation of active HCV infection, given the large number of seroreactive specimens tested annually, we evaluated the Ortho trak-C assay (OTCA) as a second-line confirmatory test and determined its limit of detection (LoD). Of 502 specimens from treatment-naïve anti-HCV-positive individuals, 478 had sufficient volumes for evaluation by the OTCA and HCV RNA tests. Core antigen was not detected in 147 of 478 (30.8%) of these specimens, of which 37 of 147 (25.2%) were shown to be viremic by the VERSANT HCV (version 3.0) (branched-DNA) assay and/or the VERSANT HCV qualitative assay. Testing of 144 replicates of a World Health Organization standard dilution series indicated that the LoD of OTCA was approximately 27,000 IU/ml. This LoD is consistent with the inability of OTCA to detect core antigen in clinical specimens with low viral loads. We conclude that OTCA has limited value as a confirmatory test for the diagnosis of active HCV infection because 37 of 367 (10%) of viremic specimens had undetectable core antigen. Qualitative HCV RNA testing remains the present standard for the confirmation of active HCV infection in the diagnostic setting.
authors.affiliation: British Columbia Center for Disease Control, 655 W. 12th Ave., Vancouver, BC V5Z4R4, Canada. mel.krajden@bccdc.ca
authors.forename: Mel
authors.initials: M
authors.lastname: Krajden
authors.forename: Rishma
authors.initials: R
authors.lastname: Shivji
authors.forename: Kingsley
authors.initials: K
authors.lastname: Gunadasa
authors.forename: Annie
authors.initials: A
authors.lastname: Mak
authors.forename: Gail
authors.initials: G
authors.lastname: McNabb
authors.forename: Michel
authors.initials: M
authors.lastname: Friesenhahn
authors.forename: David
authors.initials: D
authors.lastname: Hendricks
authors.forename: Lorraine
authors.initials: L
authors.lastname: Comanor
mesh_terms: D002170:Canada; D016174:Hepacivirus / Q000302:isolation & purification*; D006526:Hepatitis C / Q000097:blood / Q000175:diagnosis*; D006801:Humans; D012367:RNA, Viral / Q000097:blood* / Q000302:isolation & purification; D012044:Regression Analysis; D012680:Sensitivity and Specificity; D014758:Viral Core Proteins / Q000032:analysis*; D019562:Viral Load
chemical_list: D012367:RNA, Viral; D014758:Viral Core Proteins