Different serologic markers or combinations of markers are used to identify different phases of HBV infection. However, the unmet need for multiple seromarkers screening challenged the clinical interpretation and also detection of atypical serological profiles. Furthermore, the absence of HBsAg in the blood of apparently healthy individuals does not rule out the absence of circulating HBV DNA, and hence occult HBV infection (OBI) increases the risk of HBV transmission and life-threatening complications.

Objective: the objective of this study was to characterize multiple HBV serological markers, associated factors, and occult HBV infection in eastern Ethiopia.

Methods: Health facility based comparative cross-sectional study was conducted from September 2017-February 2018 in ART clients and HIV negative adults in Dire Dawa, Jigjiga and Harar towns. The research protocol was reviewed and approved by Haramaya University Institutional Health Research Ethics Review Committee (IHRERC) and Armauer Hansen Research Institute/All Africa Leprosy Rehabilitation and Training Center (AHRI/ALERT) ethics review committee. Data were collected using a structured questionnaire. HBsAg, anti-HBc and anti-HBs were detected from plasma using enzyme linked immunosorbent assay (ELISA). DNA extraction, amplification and quantification were conducted from isolated anti-HBc (IAHBc) individuals using the available RealTime PCR plat form (Abbott m2000rt, Germany). Data were double entered using Epidata software version 3.1 and analyzed using Stata software version 13. Descriptive and binary logistic regression analyses were conducted.

Results: A total of 1818 (901 HIV positive and 917 HIV negative) individuals were included. The overall HBsAg prevalence was found to be 12.7% [95%CI (11, 14)]. The prevalence was 11.7% [95%CI (10, 14)] and 13.6% [95%CI (11,16)] among HIV positive individuals on ART and HIV negative adults, respectively. A total of 868 (47.7%) participants had shown evidence of previous HBV exposure. Of the total screened, 660 (38.4%) were negative for all and therefore susceptible to HBV infection, 385 (22.2%) were immune due to natural infection, and 146 (8.4%) had chronic HBV infection without prior knowledge of their HBV status. Among the ART clinic attendants who were coinfected with HBV (HBsAg positive), 45.7% were not receiving the appropriate ART regimen. Of the 306 (17.6%) of the total individuals positive only for anti-HBc (IAHBc), 224 (73.2%) had successful HBV DNA extraction and quantification. Among these, 13 (5.8%) of them had HBV DNA (OBI), of which 5.6% were HIV negative and 6% were HIV positive individuals. The HBV DNA concentration among the OBI was <200IU/ml, indicating true occult HBV infection.

Sex, level of education, history of hospital admission, sharp tools injury, tattooing, multiple sexual partners, genital discharge, and sharing sharp tools were significantly associated with HBV infection (p<0.05). HBsAg seropositivity was lower among clients who had been taking cART containing tenofovir (TDF) (p<0.05).

Conclusion: This study found a relatively higher burden of HBV infection among unaware individuals. Multiple seromarkers detection improves clinical significance by identifying chronic HBV infected individuals that may require treatment and/or further follow-up and individuals with atypical serological profiles. The study also reported the proportion of HBsAg negative individuals with HBV DNA in their blood (OBI), that may transmit the virus.

Key words: HBV, HBsAg, anti-HBc, anti-HBS, HBV seromarkers, Occult HBV Infection