Are VIDAS® anti-HEV IgM and IgG assays fit for reliable diagnosis of hepatitis E virus infections? Comparison & case story telling

Objectives: Hepatitis E virus (HEV) genotype 3 is an emerging pathogen in developed countries. We evaluated the performance of two new serological assays for the detection of HEV, VIDAS® anti-HEV IgM and IgG. Methods: VIDAS® assays were performed on 77 clinical samples: 68 samples from patients suspected for HEV infection and 9 samples which previously tested positive for HEV IgM, IgG or HEV PCR. All samples were also tested using Wantai HEV assays. Cross-reactivity was assessed. To get a better view on the natural course of HEV infections, three clinical cases are described. Results: The concordance rate between VIDAS® and Wantai assays was good for HEV IgM (0.75,CI 0.52-0.98) and very good for HEV IgG (0.85,CI 0.72-0.98). Four samples tested borderline/positive with Wantai IgM but negative with VIDAS® IgM. All of these samples were HEV RNA negative, HEV IgG was positive in 2/4 samples. Five samples produced conflicting HEV IgG results. These tested positive with VIDAS® but negative with Wantai IgG. All five samples were HEV IgM and RNA negative. We detected no cross-reactivity. The clinical cases illustrate that HEV serology can still be negative in the very beginning of an acute infection. Conclusions: There is a good agreement between VIDAS® and Wantai anti-HEV IgM and IgG assays. Discrepant HEV IgM results probably reflect false positive Wantai IgM results (RNA-/IgG- samples) and longer-lasting positive Wantai IgM (RNA-/IgG+ samples). Discrepant HEV IgG results, could either represent resolved HEV infections (false negative Wantai IgG results) or false positive VIDAS® HEV IgG results.