Study design and setting
We conducted a cross-sectional study among women receiving antenatal care (ANC) in Primary Health Centres (PHCs) of Gamawa LGA, Bauchi State between March and April 2018. Gamawa LGA has an estimated projected population of 427,761 (2018).8 It is a rural LGA and farming is the predominant occupation of the people. The LGA has 18 political wards and 62 PHCs out of which 24 offered ANC services. Among the PHCs that offered ANC, the services were offered once weekly in most of the health facilities and average ANC attendance was 30 clients per facility per day.
Sample size determination
We calculated a sample size of 210 using the formula for cross sectional studies16 based on the documented HBsAg prevalence of 14.1% among pregnant women in Nigeria3 at 95% confidence interval (CI), 0.05 precision and 10% non-response rate.
We employed multistage sampling method to recruit 210 pregnant women. At the first stage, we recruited eight health facilities (HFs) from the list of 24 HFs that provide ANC using balloting method of simple random sampling. At the second stage, we recruited patients attending ANC in the selected hospitals using systematic random sampling. We planned to collect the sample over 8 weeks. Using the average daily attendance to ANC in the selected hospitals, we estimate a sampling interval of 10. The first attendee is sampled by balloting and subsequently every 10th attendee was approached for the study till the sample size was achieved. After explained the purpose of the study, written informed consent was obtained, the questionnaire was administered and one millilitre of blood sample was collected through an aseptic venipuncture for HBV serology.
Study instrument and data collection
The participants were interviewed by the investigator and research assistants using a semi-structured questionnaire to obtain information on socio-demographic characteristics, history of vaccination, blood transfusion, surgery, tonsillectomy, dental procedure, sharing of needles, and history of cupping, scarification and episiotomy. The questionnaires were both in English and Hausa. After this one millilitre of blood was collected aseptically for hepatitis B serology. We excluded ANC attendees that were not residing in Gamawa LGA.
HBsAg was assayed using an enzyme-linked immunosorbent assay (ELISA) kit produced by LabACONR (Hangzhou Biotest Biotech Co., Ltd, China) which has sensitivity and specificity of 99.9% and 99.0% respectively. The kit has in-built controls and the manufacturer’s instruction were closely followed. The results were reported as positive or negative.
Data analysis was performed using Microsoft Excel and Epi-info 7.2. We estimated the proportion of the patient that were positive to HBsAg, frequency and proportion of the various sociodemographic and clinical characteristics. We examined the relationship between the HBsAg status and the sociodemographic and clinical characteristics using the chi square statistics at the 95% confidence interval.