Does the ultrasensitive HBsAg Next assay enhance Hepatitis B diagnosis? An evaluation of analytical performances

Accurate laboratory confirmation for Hepatitis B diagnosis and monitoring are crucial. Recently an ultrasensitive immunoassay test, the HBsAg Next (HBsAgNx), has been reported approximately eight times more sensitive than current HBsAg assays. The aim of our study was to assess the analytical performances of this new test. 253 clinical samples from Saint Louis University Hospital were analyzed, splitted into four panels: [1] routine prospectively screening serums (n=196), [2] retrospective serum samples before HBV reactivation (HBV-R) (n=18), [3] occult HBV infection (OBI) (n=10) and [4] a selection of wild type HBV genotypes (n=29) Panel 1, showed robust agreement with the HBsAg Qualitative II assay (Cohen's kappa = 0.83). Despite this agreement, 7 false positive with the Qualitative II assay were found negative with HBsAgNx. One OBI was detected only with HBsAgNx. Panel 2 showed potential time savings in diagnosing HBV-R using HBsAgNx among 4/18 HBsAg positives samples. Panel 3 highlighted the ability of HBsAgNx to detect HBsAg in OBI patients defined by negative for HBsAg with Qualitative II assay and positive for HBV DNA. Furthermore, the HBsAgNx assay detected all different genotypes. The study highlights the effectiveness of the HBsAgNx assay, showing its performance. It excels in detecting weakly positive samples and addressing challenging cases. HBsAgNx assay demonstrates promising analytical performances, with improved sensitivity and specificity compared to standard HBsAg Qualitative II assays, able to detect all genotypes. Its potential impact on early detecting and monitoring reactivations, and occult infections could be very useful in clinical practice.