Clinical Value of Total HCV Core Antigen Detection and Quantification

Recently, use of the total HCV core antigen assay in peripheral blood has gained more interest in clinical evaluation of HCV patients. The aims of the present study were to assess the value of total HCV core antigen as a marker of viral replication, to determine the sensitivity of the core antigen assay relative to molecular biology technique and to establish a relationship between HCV core antigen and HCV RNA units.

This study included 150 patients seropositive for antibodies to HCV. Viral load was assessed by both HCV RNA quantitative assay (bDNA) and HCV core antigen quantitative immunoassay (Ortho trak-C assay). Spearman rank correlation coefficient was used to determine significant correlations among parameters.

Of the 150 studied patients, 128 (85%) were positive to HCV RNA assay (bDNA) and 22 (15%) were negative. Among the 128 patients who tested positive for HCV RNA, 125 patients tested positive by HCV core antigen assay with a sensitivity of 98%. All patients who tested negative for HCV RNA assay (bDNA) gave negative results by HCV core antigen assay with a specificity of 100%.

In the 125 patients that were positive by both assays, HCV RNA and total HCV core antigen were significantly related (r = 0.984; p< 0.001). The relationship between HCV RNA in IU/ml and total HCV core antigen in pg/ml was given by the following equation: Log HCV core antigen = 0.649 x Log HCV RNA - 2.018. It was found that 1 core pg/ml is equivalent to approximately 8000 HCV RNA IU/ml in clinical samples of the studied patients.

The correlation between HCV RNA IU/ml and HCV core antigen pg/ml varied around this average ratio when individual samples were considered, with the majority of the ratios lying between 5000 and 13000 HCV RNA IU/ml per core pg/ml.

To evaluate the clinical use of total HCV core antigen quantification in the pretreatment assessment and in monitoring the response to interferon therapy, sera from ten patients who were treated with a combination therapy of interferon alpha-2a and ribavirin were studied. Serum samples were collected at baseline, 12 weeks after initiating therapy and at the end of treatment to be tested by both assays.

There were significant correlations between log HCV RNA titer (IU/ml) and log HCV core antigen (pg/ml) (r = 0.693, 1.0 and 1.0 for the three comparisons respectively; p< 0.031, 0.003, and 0.017 respectively).

The authors of the study conclude, “The HCV core antigen assay can be used in confirming HCV infection when antibodies have been detected, in screening patients, and in monitoring therapeutic interventions.”

05/26/04

Reference
M M Omar and others. Clinical Value of Total HCV Core Antigen Detection and Quantification. Abstract 2039 (poster). Digestive Disease Week 2004. May 15-20, 2004. New Orleans, LA.