Objectives: To evaluate the sensitivity and specificity of IgM to recombinant antigen E2 of HEV envelope protein in the diagnosis of acute sporadic hepatitis E.
Methods: anti-E2 IgM was detected in sera samples from 176 cases of acute sporadic hepatitis E and 191 cases of acute non A-E hepatitis by ELISA and was compared with HEV IgM detected by some domestic and Genelabs (GL) kits. HEV RNA was also detected in sera positive for anti-E2 IgM. Logistic regression was used to analyze factors associated with the detection of anti-E2 IgM and HEV RNA.
Results: Anti-E2 IgM was found in 68.75% of the serum samples from the 176 patients of acute hepatitis E and the positive rate of HEV IgM detection by domestic kits was 56.25% (chi2 IgM = 6.49, P < 0.05). There were 37 (19.37%) anti-E2 IgM positive cases in those 191 sera of the acute non A-E hepatitis, out of which 11 cases were also detected as positive by the GL kit. Of the 158 anti-E2 IgM positive sera, HEV RNA was found in 81 (51.27%), among which 57.02% was positive in acute hepatitis E and 32.43% in acute non A-E hepatitis. No HEV RNA was found in the anti-E2 IgM negative sera from the cases of acute hepatitis E. By logistic regression analysis, no variance relative to the detection of anti-E2 IgM was found with the time interval from onset to hospitalization, age, levels of bilirubin, ALT and AST of the serum. Only the level of serum ALT was found being significantly associated with the detection of HEV RNA (P = 0.024).
Conclusions: (1) anti-E2 IgM is a sensitive and specific serological maker for diagnosing an acute infection of HEV. (2) HEV is still the pathogen of some cases diagnosed clinically as non-A-E hepatitis. (3) Persistent HEV viremia is possibly an important factor influencing the severity of acute hepatitis E.