Assay Sensitivity Difference Can Induce Anti-Hepatitis A Virus IgM Non-Reactive But Total (IgM and IgG) Reactive Results in Early Acute Hepatitis A.

Although anti-hepatitis A virus (HAV) IgM non-reactive and anti-HAV total (immunoglobulin [Ig] M and IgG) reactive results are generally interpreted as immunity to HAV, some early acute hepatitis A patients show the same results. We compared IgM detection sensitivity between anti-HAV IgM and anti-HAV total assays. Acute hepatitis A patients' samples were serially diluted and tested with Elecsys anti-HAV IgM and total assay (Roche Diagnostics). This resulted in anti-HAV IgM non-reactive but anti-HAV total reactive results. Samples of two hepatitis A patients showing false-negative anti-HAV IgM at initial presentation were analyzed with Elecsys, Atellica (Siemens Healthineers), and Alinity (Abbott Laboratories) HAV assays. Elecsys, Atellica, and Alinity anti-HAV IgM converted reactive on hospital day 3, whereas Elecsys and Atellica anti-HAV total results were reactive from hospital day 1. The anti-HAV total assay had higher sensitivity in detecting IgM antibodies than the anti-HAV IgM assay.