36 Institutional Adherence to CDC Guidelines for Hepatitis C Virus Screening Reveals Added Utility of Confirmatory Molecular Testing

Abstract

Current Centers for Disease Control and Prevention (CDC) recommendations for hepatitis C virus (HCV) screening include confirmation of reactive HCV antibody (HCVAB) results for all patients and confirmation of nonreactive results for patients who may have been exposed within the past six months. Our aim was to assess adherence to these recommendations at a 1,250-bed tertiary care hospital in the Midwestern United States. In cases for which confirmatory testing was performed, our secondary aim was to determine the accuracy of the HCVAB screen for the assessment of active HCV infection. We retrospectively identified consecutive HCVAB samples tested by the ADVIA Centaur Immunoassay System over a period of seven years (January 2010 to December 2016) and by the COBAS AmpliPrep/COBAS TaqMan HCV RNA viral load assay (HCVRNA) over the same time period. The HCVAB test results were recorded as well as the percentage of reactive and nonreactive results that received confirmatory testing within 30 days. When both tests were performed, we calculated the concordance rates. Using the HCVRNA as the gold standard, we calculated the positive predictive values (PPVs) and negative predictive values (NPVs) of the HCVAB for the detection of active HCV disease within the patient population receiving both tests within 30 days of each other and within the patient population receiving both tests within one day of each other. Over the seven-year period, 66,066 samples were tested for HCVAB; 61,976 (93.8%) were negative, and 4,090 (6.2%) were positive. Of the 4090 HCVAB samples with positive results, 3,607 HCVAB samples underwent HCVRNA testing within 30 days, suggesting 88.2% adherence to CDC guidance for confirmation of positive HCVAB results. Of the 61,976 negative HCVAB results, 1,888 (3.0%) received confirmatory HCVRNA testing within 30 days. Among the 5,495 HCVAB samples followed up by HCVRNA testing within 30 days, there were 892 false-positive (HCVAB-positive, HCVRNA-negative) and 171 false-negative (HCVAB-negative, HCVRNA-positive) results, leading to a HCVAB PPV/NPV of 75.3%/90.6%. When the analysis was limited to HCVAB/HCVRNA test pairs that were taken within 1 day of each other (n = 1,790), the PPV/NPV improved to 78.6%/96.0%. The adherence to CDC confirmatory recommendations for patients with positive HCVAB results is high (88.2%), and a large proportion of patients with negative HCVAB results do not receive additional testing (97.0%). A small but significant proportion of patients with negative HCVAB tests will have a positive viral load within 30 days and even within one day. Although repeat testing in our study was likely to occur primarily among high-risk patients, creating the potential for bias, these findings suggest that patients with ongoing risk factors for HCV should receive follow-up testing with HCVRNA quantification.