Optimized commercial enzyme immunoassays may be able to diagnose hepatitis B virus (HBV) using oral fluid samples, according to study results published in BMC Infectious Diseases.

It is estimated that there are 257 million chronic HBV carriers worldwide, which highlights the substantial health, social, and economic burden of HBV. Currently, HBV infection diagnosis is performed using serum and plasma samples collected via venipuncture, which can be invasive, expensive, and potentially painful and arduous for some individuals including the elderly, obese, patients receiving hemodialysis, and drug users. The use of oral fluid samples as a noninvasive alternative may be promising, because saliva from salivary glands and gingival crevicular fluid is a transudate plasma derived from the capillary bed beneath the tooth-gum margin, making obtaining samples easy and noninvasive. However, a drawback to obtaining these samples may be that the concentration of IgG in oral fluid has been reported to be an average of 300 times lower when compared with the concentration in serum.

Markers for HBV have been detected in oral fluid samples previously, specifically the surface antigen of the hepatitis B virus (HBsAg). But few studies have evaluated the utility of oral fluid samples in detecting antibodies directed against the core protein of HBV (anti-HBc). Therefore, this study optimized 1 commercially available assay for detecting total anti-HBc marker in oral fluid samples and evaluated its utility under real life conditions in different settings for the purposes of prevalence and diagnostic studies.

Oral fluid was collected with a Salivette® device (Sarstedt AG & Co. KG, Nümbrecht, Germany) and parameters including type of elution buffer and sample volume were evaluated. Once this assay was optimized, the study included 1296 subjects primarily aged <40 years (53.3%) who had completed high school (29.6%) and did not have hepatitis C virus. All subjects provided serum and oral fluid samples that were evaluated for detection of anti-HBc. All serum samples were submitted to commercial enzyme immunoassays to detect total anti-HBc according to the manufacturer’s instructions and oral fluid samples according to previous optimization.

Optimization found the best elution buffer was PBS/BSA 0.5% and the best oral fluid sample volume was 100 µL. Using these optimized parameters, 1085 of the samples collected from the 1296 participants did not detect anti-Hbc; in 211 samples, anti-HBc was detected. The oral fluid sensitivity was 52.6% and specificity was 96%. Sensitivity was higher in patients presenting with an active HBV infection compared with anti-HBc isolate and past infection, 92.7%, 43.2%, and 36.9%, respectively. In addition, sensitivity was higher in participants without active hepatitis C virus infection and also in participants who used injection drugs (85.9%).

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Overall, the study authors concluded that, “In conclusion, it was possible to optimize a commercial [enzyme-linked immunosorbent assay] for detecting anti-HBc in oral fluid samples where the highest concordance was found in ambulatory settings and among individuals with active infection.”

Reference

Cruz HM, de Paula VS, da Silva EF, et al. Utility of oral fluid samples for hepatitis B antibody detection in real life conditions [published online July 17, 2019]. BMC Infectious Diseases. doi:10.1186/s12879-019-4183-0