Evaluation of saliva specimens as an alternative sampling method to detect hepatitis B surface antigen

In this study, a modified enzyme immunoassay (EIA) was evaluated for the Hepatitis B surface antigen (HBsAg) among whole saliva and oral fluid samples. Specimens were collected from 115 individuals who gave serum and oral fluid using Salivette (Sarstedt, Nümbrecht, Germany) and whole saliva. Saliva specimens were tested following a modified ELISA, and the results were compared with paired serum specimens that were tested according to the supplier's instructions. Transport buffer for the oral fluids, sample volume for assay, incubation period of sample with conjugate as well as cut-off values were evaluated to optimize the assay. The highest sensitivity and specificity were obtained by increasing the incubation of sample and conjugate to 16  hr and using the area under the receiver operating characteristic curve to calculate cut-off values. HBsAg was detected in 40 oral fluids and 44 whole saliva samples out of 47 paired positive serum specimens and not detected in 64 oral fluids and 63 whole saliva samples out of 68 matched negative sera samples by the ELISA assay. There was excellent agreement between the results for the serum and saliva specimens kappa value (κ): 0.80 for oral fluid and κ: 0.87 for whole saliva and there was excellent reproducibility. Using an optimized protocol, the sensitivities of whole saliva and oral fluid were 93.6 and 85.1%, respectively, whereas specificities of whole saliva and oral fluid were 92.6 and 94.1%, respectively. Our data showed a significant promise for the use of whole saliva and oral fluid together with the modified commercial EIA for Hepatitis B virus infection surveillance.