In order to determine the efficacy of a new hepatitis B immune globulin (HBIG), a phase 3, vertical transmission (mother to child) clinical interventional trial of hepatitis B virus (HBV) post exposure prophylaxis (PEP) was conducted at selected sites (n=15) throughout India. This required a large screening program for HBsAg positivity at prenatal clinics located in tertiary care hospitals. 36,379 pregnant women consented to be tested for Hepatitis B surface antigen (HBsAg) by Rapid Test and if positive-confirmed by ELISA. The weighted mean prevalence was 0.82% (95% CI, 0.72, 0.91). In conclusion, the prevalence of HBV carrier state during pregnancy in India in this study was low compared to previous reports.

Key Words: Hepatitis B, India, Pregnancy, Prevalence.

This study was conducted from November 2003 to July 2006. For the purpose of this short communication, the epidemiological data from the screening tests performed in 36,379 pregnant women at 15 centers will be reported. Study centers were selected for the study on the basis of expected screenings or enrolments into the study. All pregnant women attending the antenatal clinics of these centers were screened for HBsAg at 5-9 months of gestation after informed consent was obtained. We used a rapid HBsAg test Kit (ACON Laboratories Inc, USA). A positive HBsAg test was confirmed by enzyme-linked immunosorbent assay (ELISA) after the pregnant woman signed the second part of an Informed Consent Form, consenting to her and her child’s participation in the study. Bioelisa HBsAg ELISA kit (Biokit, Barcelona, Spain) were used according to the manufacturer’s recommendations for HBsAg detection and absorbance was measured using an ELISA reader (MRX Microplate Reader, Dynatech, USA). The study was approved by DCGI (Permission No from DCGI: 12-51/2003-DC) and hospital ethics committees at each of the 15 institutions involved in this study, and the study was conducted in accordance with the ethical principles of the Declaration of Helsinki, and in accordance with the International Conference on Harmonization (ICH) of Technical Requirements for Registration of Pharmaceuticals for Human Use, E6 Good Clinical Practices: Consolidated Guidelines, Food and Drug administration (FDA) regulations and IEC-required procedures.

This large scale screening program in 15 tertiary care hospitals throughout India identified 398 (Table I) HBsAg positive women allowing some epidemiological data to be collected of the prevalence of HBV carrier state during pregnancy across all represented populations in India.

TABLE I



Prevalence of HBsAg at Prenatal Screening

Statistical analysis: The number of patients in each study center varies so the mean might deliberately over-represent or under-represent certain segments of the population. To restore balance of the number of patients enrolled in each center, the prevalence of HBsAg positivity was estimated using a weighted pooled point estimate along with a 95% confidence interval(5). Using this method, less weight will be placed on the study center with smaller number of enrolled patients and greater weight on the study center with larger number of enrolled patients. All calculations were performed using SAS® version 8.2. RNTMC screened 472 subjects and 0 tested HBsAg positive by screening test kit, the prevalence rate at this center was corrected to read 0.001 in order to include this data into the formula for weighted prevalence rates (Table I).

Out of 36,379 pregnant women screened, 406 were HBsAg positive by rapid screen Further testing of these 406 positive tests determined that 398 were positive by ELISA. Thus the false positivity rate of the rapid screen is 2%.

The range of prevalence of HBsAg positivity in pregnant women varied from 0.4% (VHBMC, Bangalore) to 4.6% (SJMCH, Bangalore) and the overall mean prevalence of HBsAg positivity was 1.09% (95% CI 0.99-1.21) and the overall weighted mean of the prevalence of HBsAg positivity was 0.82% (95% CI 0.72-0.91). It has been confirmed that the high prevalence of HBsAg positivity at SJMCH in Bangalore was due to pre-selection of the population at this hospital since it is a referral center for "infectious cases" for the area. The mean prevalence of HBsAg positivity and weighted mean of the prevalence of HBsAg positivity excluding SJMCH prevalence rate was calculated to be 1.05% (95% CI 0.95-1.16) and 0.81% (95% CI 0.72-0.90), respectively.

The prevalence of HBsAg positivity in pregnancy which was observed in this prospective, intervention study is less than 50% of previously reported non-tribal prevalence rates in systematic review of literature(2,3). The main limitation of the study is that the centers were located in urban areas and these centers were tertiary care referral centers. However, volunteer patients were not selected on the basis of referrals or walk-ins from the surrounding areas and not referrals except SJMCH, Bangalore. There is little change in weighted mean prevalence of HBsAg positivity excluding SJMCH (0.81%) compared to the overall weighted mean prevalence of HBsAg positivity including SJMCH (0.82%). This sample of patients screened and enrolled into the study may not be representative of the prevalence of hepatitis B infection in rural areas but is representative of the prevalence in urban areas.

The HBsAg rapid screen (Rapid Test Kit ACON Laboratories Inc, USA) was accurate in 98% of cases when used in a mass screening program of this nature and may be a cost effective means of screening pregnant women for HBsAg to identify at risk populations eligible for immunoprophylaxis of their neonates.

The weighted mean prevalence of HBsAg positivity in our multi-center prospective study was 0.82%, which is roughly less than one half of the previously reported point prevalence of HBsAg carrier state in non tribal populations in India(3). Consequently, the pharmaoeconomics of imple-menting an immuno-neprophylaxis program consisting of testing all pregnant mothers for HBsAg status and the administration of HBIG and recombinant hepatitis B vaccine within 12 hours of delivery to at risk neonates across the India may roughly be one half the previously estimated costs.

Contributors: All authors contributed to the study design, concept, literature search, data analysis and drafting of the manuscript.

Funding: Cangene Corporation, Winnipeg, Manitoba, Canada.

Competing interests: Cangene Corporation provided study grant to the participating 15 tertiary care hospitals in India.

All the investigators contributed greatly to the successful completion of this large clinical trial and the principal authors wish to recognize the team for this large scale screening effort and collection of the epidemiological data reported above (Annexure).