Occult hepatitisB infection in Tunisian pregnant women

Abstract number: P2001

Hannachi N., Bahri O., Mhalla S., Triki H., Boukadida J.

Objective: In Tunisia, the national screening programme for identification of hepatitis B virus (HBV) infection in pregnant women is based on HBs antigen (HBsAg) test. HBV-DNA in the serum can be detected in the absence of HBsAg in case of occult hepatitis B infection. The objective of this study is to evaluate the prevalence rate of occult hepatitis B in healthy pregnant Tunisian women.

Methods: During one year period (September 2007 to September 2008), a total of 2709 pregnant women were prospectively screened for HBsAg and anti-HBc antibody (anti-HBc). Negative HBsAg sera were systematically tested for anti-HBs antibody (anti-HBs). Detection of HBV-DNA was performed for "anti-HBc isolated" sera. The presence of HBV genome was tested by a single-step PCR in Pre-S gene and a nested PCR in X region. The sensitivity of the PCR assays was evaluated using samples with known viral load.

Results: Seroprevalence of positive HBsAg was 4%. Vaccinal immunity was detected in 3% of HBsAg negative women. Anti-HBc was detected in 22% of pregnant women (including HBsAg positive women). Anti-HBc was associated with anti-HBs in 13.5% and isolated in 4.5% of total pregnant women. Among 123 women with anti-HBc isolated marker, anti-HBs concentration varied between 5 and 10 mUI/ml in 19 women. Detection of HBV-DNA was performed in 98 cases (with anti-HBs lower than 5 mUI/ml) and was positive in three cases (3%) by the two PCR assays. Sensitivity of HBV-DNA detection was 10³ copies/ml.

Conclusion: occult hepatitis B can be misdiagnosed by selective HBsAg screening in pregnancy. This can lead to a lack of appropriate prophylaxis in newborns. Anti-HBc antibody should be tested routinely on pregnant women especially in a country of intermediate endemicity for HBV infection. More effort is needed for HBV vaccination strategies in Tunisian women.