Increased Need for Testing to Confirm Initial Weakly Reactive Results for Hepatitis B Virus Surface Antigen

Abstract

Objectives: To examine the agreement between results of initial testing and those of confirmatory testing for the presence of hepatitis B virus surface antigen (HBsAg) via electrochemiluminescence immunoassay (ECLIA). This study also sought to evaluate the applicability of confirmatory testing for HBsAg detection via ECLIA and to establish the gray zone within which a confirmatory test is needed. Methods: Specimens collected between April 2009 and July 2010 that yielded COI values between 0.9 and 10.0 as determined by HBsAg ECLIA testing were subjected to confirmatory testing to evaluate the appropriate threshold for HBsAg confirmation. Receiver operating characteristic (ROC) analysis of the confirmatory test results were used to establish the COI gray zone for the initial test results, with the goal of determining when confirmatory testing is required. Results: Of the 144 specimens with COI values between 0.9 and 10.0, all of those with negative confirmatory testing results had COI values of 0.9 to 4.0. Specimens that required confirmatory testing had results within a COI gray zone range of 1.0 to 4.0 in HBsAg initial testing. Conclusion: Confirmatory testing to detect HBsAg is essential for specimens that produce weak initial HBsAg signals (ie, which had initial COI values of 1.0–4.0), as determined by ECLIA because the initial test results can include false positives. ROC analysis established a COI range for initial HBsAg test results providing the range of concentrations over which a confirmatory test is required. * HBV : hepatitis B virus CHB : chronic hepatitis B HBsAg : hepatitis B virus surface antigen ECLIA : electrochemiluminescence immunoassay COI : cutoff index S/CO : sample to cutoff S/N : counts per minute of sample/mean counts per minute of negative controls ROC : receiver operating characteristic