FROM THE JOURNAL OF INFECTIOUS DISEASES
While real-time polymerase chain reaction (PCR) testing is the standard test for hepatitis E virus infection, an anti-HEV-specific enzyme-linked immunosorbent assay (ELISA) is more effective than is PCR at distinguishing between acute and chronic HEV infections.
“A clinical challenge in the management of immunocompromised patients with HEV infection is to differentiate between the acute and chronic course of infection [as] approximately 60% of infected immunocompromised individuals experience a chronic infection, which might require treatment with ribavirin,” said lead author Patrick Behrendt, Dr.med., of Hannover (Germany) Medical School.
The anti-HEV antigen (Ag) ELISA has recently become commercially available, making it an even bigger matter of interest. Dr. Behrendt and his coinvestigators analyzed sera from 18 patients with acute and 21 patients with chronic HEV, whose samples were collected between 2008 and 2015. The sera were retrospectively analyzed via both real-time PCR and ELISA to compare the efficacy of each in identifying HEV – more specifically, HEV genotype 3 – in each subject. For the ELISA analysis, 100 mcL of serum were added to each well of an ELISA plate, which was subsequently incubated at 37 degrees Celsius for 1 hour.
The researchers analyzed sera from four individuals with chronic HEV using serial dilutions to compare sensitivity of real-time PCR and ELISA. In three out of those four sera (75%), ELISA showed negative results due to HEV RNA levels of fewer than 10,000 copies/mL; on the other hand, real-time PCR showed a “linear reduction in levels,” indicating that it is the better option in detecting HEV genotype 3 ( J Infect Dis. 2016 May 27;214:361-8 ).
ELISA was also used on 20 chronic HEV patients and 17 acute HEV patients to determine its sensitivity at distinguishing between the two types of infection. In this cohort, only 64.7% of RNA-positive patients were deemed positive according to the ELISA testing, while ELISA results were positive in all of the cases of chronic HEV infections. None of the patients with chronic infection registered a false-negative, which indicates “a high reliability of the assay for this cohort,” according to the investigators.
“Comparison of chronically infected individuals with acutely infected patients revealed drastically increased ODs in chronically infected patients, while most of the positive samples from acutely infected patients displayed significantly lower values [which] led to a sensitivity of 100% (20 of 20) [ELISA] results for chronically HEV infected individuals,” the authors concluded. “Our study demonstrates that [ELISA] has a sensitivity of 65% and a specificity of 92% in detecting an ongoing HEV infection in a real-life cohort.”
The German Center for Infection Research, the Helmholtz Center for Infection Research, and the German Ministry for Education and Research funded the study. The researchers reported no relevant financial disclosures.