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Saliva-based assay successfully tests for hepatitis E

Newly developed oral fluid-based immunoassays had high concordance with commercial high-performance serum enzyme-linked immunosorbent assay kits in testing for recent or prior hepatitis E infection, according to a recently published study.

“Oral fluid collection requires fewer resources than blood collection since no clinically trained personnel are needed. Moreover, oral fluid can be self-collected and returned by mail/courier,” Nora Pisanic, PhD, from the John Hopkins Bloomberg School of Public Health, Baltimore, and colleagues wrote. “These attributes could help fill gaps in infectious disease surveillance in populations typically underrepresented in health research including those in remote and resource-limited settings and children and pregnant women.”

The study comprised a group of patients referred to a diagnostic center in Dhaka, Bangladesh, for symptoms of acute viral hepatitis (n = 76) and a group of patients referred for other reasons to act as controls (n = 65).

All participants provided a blood sample, two saliva samples (one self-collected and one collected by clinical staff), and answered a short questionnaire regarding sample collection preferences and symptom characteristics. The researchers used enzyme-linked immunosorbent assay kits developed by Beijing Wantai Biological Pharmacy Enterprise as reference to validate the Environmental Health, Microbiology and Immunology Lab (EHMIL) serum- and saliva-based assays developed in this study.

The EHMIL serum HEV IgG antibody assay had a sensitivity between 98.7% and 100% and specificity between 96.8% and 100%, depending on the method of signal adjustment used.

The EHMIL serum HEV IgM assay had a sensitivity of 94.7% with one discrepant sample and specificity of 98.3% with two discrepant samples, regardless of signal adjustment method. Sensitivity of the EHMIL HEV IgA assay, tested with both serum and saliva, ranged from 94.7% to 100% and the specificity from 98.3% to 99.1%, depending on signal adjustment method.

All self-collected and staff-collected saliva samples were correctly classified when compared with the reference kits with only minimal differences between self- and staff-collected HEV IgG negative samples.

Results of the questionnaire showed that the patients preferred to self-collect the saliva sample vs. having a clinician collect it (96.5%), preferred to provide a saliva sample vs. blood (90.8%), and preferred to send a self-collected sample by mail or drop it off at a hospital vs. having it collected by clinical staff at a hospital (92.2%).

“Even if saliva-based hepatitis E testing is not more accurate than existing serologic hepatitis E tests, it opens the door for large-scale population-based cross-sectional and longitudinal studies of hepatitis E incidence and prevalence,” the researchers concluded. “Saliva-based hepatitis E incidence and prevalence estimation could reveal the underlying immunological landscape of HEV infection and inform novel prevention strategies in endemic and resource limited settings that experience large-scale epidemics.” – by Talitha Bennett

Disclosure : One author (D.A. Granger) reports he is the founder and chief scientific and strategy advisor for Salimetrics and SalivaBio. Another author (S.A. Granger) reports he is chief scientific officer at Salimetrics.