Detection of markers of hepatitis B and D virus infection in biological media and dried blood spots

The aim of this study was to assess the rates of detection of the major markers of infection with hepatitis B and Delta (D) viruses in serum, saliva and dry blood dots (DBS) as a possible option for serological studies among the population of the endemic region in conditions of limited laboratory resources. For this purpose, paired samples of blood serum and DBS, blood serum and saliva from patients with chronic hepatitis B with Delta agent living in the Republic of Tyva, which is endemic for this disease. HBsAg was detected in 289 (100%) serum samples, in 88/92 (95.7%) saliva samples, in 60/80 (75%) DBS samples, stored three years at room temperature, and in 111/117 (94.9%) DBS stored one year at the same conditions. Anti-HBcore was detected in 209 (100%) serum samples, while in saliva and DBS samples this marker was detected in only 13.04% (12/92) and 19.7% (23/117), respectively. Anti-HDV antibodies in serum were detected in 209 (100%) samples collected from patients in 2017-2018. In saliva and DBS anti-HDV were not detected in any sample. This difference in the detection rates of anti-HBcore and anti-HDV might be accounted for the fact that the HBV core protein is a very strong immunogen, indusing the production of anti-HBcore in high concentrations. Probably, the concentration of anti-HDV is much lower, which explains its absence in saliva and DBS in patients with hepatitis B+D. Samples of biological media (saliva), as well as DBS can serve as an alternative material for the detection of HBsAg in screening and research prevalence studies. Meanwhile, the definition of anti-HDV in such media is not possible due to the false negative results. Due to the high probability of superinfection with HDV in patients with HBV in endemic areas, the detection of HBsAg in alternative media (saliva or DBS) should be followed by testing for anti-HDV in serum samples.