Evaluation of the core antigen assay as a second-line supplemental test for diagnosis of active hepatitis C virus infection.
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.
Krajden
Mel
M
British Columbia Center for Disease Control, 655 W. 12th Ave., Vancouver, BC V5Z4R4, Canada. mel.krajden@bccdc.ca
Shivji
Rishma
R
Gunadasa
Kingsley
K
Mak
Annie
A
McNabb
Gail
G
Friesenhahn
Michel
M
Hendricks
David
D
Comanor
Lorraine
L
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
D012367:RNA, Viral; D014758:Viral Core Proteins