Background: Hepatitis B virus (HBV) co-infection with HIV is becoming a major challenge due to shared routes of transmission. The co-infection rate is especially high in sub-Saharan Africa, where the two infections are prevalent; therefore, screening HBV in HIV-infected individuals should be a routine clinical practice. In Ethiopia practice of routine HBV screening, Use of HAART regimens with dual Anti-HIV/HBV action & their effect on HBSAg sero reactivity is not well studied. Objective: To determine the sero prevalence of HBSAg in HIV-infected patients, Pattern of HAART use in Co infected patients & Effect of HAART on HBSAg seroreactivity Methods: A Six years Retrospective review of HIV infected patients for whom HBSAg testing was done previously was taken by reviewing the medical records of 424 patients following in ART clinic of Ayder referral hospital from January 1 ,2009 –January 15, 2016,128 patients were found to have HBSAg test results & 110 patients were included in the study. Data was collected from the medical records of patients based on structured check list & repeat testing of HBSAg was done for co-infected patients by rapid HBSAg screening technique. Data was entered & analyzed by SPSS version 21 software; Univarate & Bivarate analysis using chisquare & binary logistic regression was done. Results: The prevalence of HBV in HIV infected patients is found to be 10% which is consistent with the prevalence worldwide & it is slightly higher than the studies done in developed countries. Among co-infected patients, 81.8% were put on HAART regimens with two active agents against HIV & HBV, which is in line with international guidelines. HBSAg Sero Conversion rate was found to be 63.6% in co infected patients who took HAART for more than one year. Conclusion: HIV/HBV Co infection rate in Ayder hospital is comparable with the previously done studies & Practice of HAART use in ARH is in accordance with International HIV & HBV treatment guidelines recommendations. All of the seroconverted patients were taking Tenofovir, Lamivudine, Efavirenz regimen proving the importance of this regimen on co infected patients.

Keywords: HBV, HIV, HAART, HBSAg, Prevalence, Ayder