The study was conducted in Kamalapur, a densely populated community in urban Dhaka, the capital city of Bangladesh. The International Centre for Diarrhoeal Disease Research, Bangladesh (ICDDR, B) has been using this as its first urban field site since 1998. It is an impoverished area comprised of seven communities in four municipal wards with 200,000 residents in an area of 4 km2 (29,663 persons/km2), 11.2% of whom are under-5 children, with a mean (range) house hold size of 4 (1 to 20) persons. They have a median monthly household income of US $50. Kamalapur is divided into seven geographical strata and 450 clusters, each with approximately 100 households. The community had all the potential reported risk factors, such as overcrowding, low income, poor sanitation for high disease burden of infectious diseases such as diarrhea, and pneumonia [26, 27] and hepatitis.
Assuming that 6% of the population will have a HBsAg positive status with 1% precision and 95% confidence limit, we estimated the sample size to be 1955. For HCV, we assumed that 5% of the population will have an anti-HCV positive status with 1% precision and 95% confidence limit, we estimated the sample size to be 1825. Assuming a refusal rate of 10%, we determined the sample size to be 2000. To get sufficient number of people to detect the above mentioned prevalence, we considered Kamalapur, Dhaka, as the population suitable for this study.
A population based, cross-sectional survey was conducted in 2000 individuals, aged 0-60 years during 2005-2006. For achieving this sample, all the 450 geographical clusters of Kamalapur were selected using random sampling. The first household of the cluster was chosen randomly and if a locked house was encountered, then the next household in same direction replaced that.
The trained field research assistants (FRAs) visited the selected households in accordance with the randomisation list and approached the head of the family. They explained the purpose and objective of the study and obtained written informed consent from study participants, or parents for eligible children. They administered a pre-tested questionnaire to the participants at a mutually agreed date at the clinic, when a research physician collected 4 ml of blood from the antecubital veins under aseptic conditions. The blood specimens were centrifuged at the clinic within 6 hours and separated sera were transported to the Dhaka Hospital of ICDDR, B, and stored at -20°C in aliquots. For diagnosis of HBV infection, HBsAg and anti-HBc were determined using commercially available enzyme-linked immunosorbent assay (ELISA) kits (Manufacturer: DiaSorin S. A., Italy). For diagnosis of HCV infection, anti-HCV antibody was detected using a third-generation ELISA kit (Manufacturer: DiaSorin S. A., Italy). After collection of blood samples, the research physician interviewed the participants (parents if the participant was a minor) in a private set up within the clinic to collect their socio-demographic characteristics including age, gender, years of education, socio-economic status, occupation, income, and marital status by using a structured questionnaire. They were also asked about the type of health care providers they consulted for health problems, history of jaundice, history of taking injections, previous surgical procedures, frequency of dental visits, receiving blood or blood products, history of current/past use of intravenous drugs, siblings, history of tattooing; ear-nose-body piercing in females, and circumcision and visiting community barbers for shaving in males. Some questions about sexual behaviour such as having multiple sexual partners, having received treatment for STD were asked to participants 18 years of age or older by research physician of the same sex. The study was approved by the Research and Ethical Review Committees of ICDDR, B.
The laboratory test results were kept confidential and the research physician shared the results with the participants. Infected individuals were provided with appropriate information on the prevention of spread of these infections to others, and referred them to the nearest public health care facilities.
We only performed HBsAg, anti-HBc, and anti-HCV to reduce the laboratory test costs.
is the serologic hallmark of HBV infection. It appears in serum 1-10 weeks after an acute exposure to HBV, prior to the onset of hepatitic symptoms. The sensitivity of HBsAg is 100%, the specificity is 99.7%, and the limit of detection is 0.05 PEI units/ml. The lower limit of detection, PEI unit was explained as the analytical sensitivity that may be expressed as the limit of detection, which is the minimal amount of specific analyte precisely detectable by the assay. A conversion of 0.05 PEI units/ml to international unit (IU) values was evaluated by testing HBsAg international reference material from World Health Organization NIBSC 1st International Standard, code 80/549; (HBsAg, subtype ad) and limit of detection was found to be 0.05 IU/ml. When the same protocol was used with Paul-Ehrlich-Institute (Germany), HBsAg reference preparation (subtypes ad, ay), the detection limit came to 0.03 PEI units/ml. If the infection is self-limited, HBsAg disappears in most patients before the serum hepatitis B surface antibody (anti-HBs) can be detected. Persistence of HBsAg for more than six months implies chronic infection.
identifies individuals with both current and past HBV infection (prevalence). The sensitivity of anti-HBc is 100%, the specificity is 99.83%, and the limit of detection is < 0.5 PEI units/ml. Almost all HBV-infected people usually develop anti-HBc. Detection of anti-HBc indicates exposure to HBV, which may be acute, chronic, or resolved infection. Fourteen (0.7%) study subjects were expressing HBsAg positive, but negative for anti-HBc. Although rare, this serological profile of HBsAg positive, but anti-HBc negative is not that exceptional. In addition to the diagnostic kits efficacy, the immunosuppressive state of the subject may also contribute to such profile .
The discovery of HCV in 1989 led to the development of an antibody diagnostic assay (anti-HCV) based on viral recombinant peptides. The third generation assays (ELISA-3) have been introduced incorporating antigens from putative neucleocapsid, NS3, NS4, and NS5 regions, and become positive in 2-3 weeks after the infection . They are currently the most widely used screening tests for HCV and are more sensitive and specific than earlier generation tests in screening blood donors . Detection of anti-HCV indicates present or previous HCV infection but cannot discriminate acute from chronic or resolved HCV infection .
All data were analysed using Statistical Package for Social Sciences (SPSS) version 10.0 . The analysis was carried out at three levels of descriptive, bivariate and logistic regression analysis. Descriptive statistics of socio-demographic variables and other characteristics of the sampled population were computed. Means and SD were calculated for quantitative variables and proportions for categorical variables. Percentage with 95% confidence interval (CI) was used to describe the prevalence. OR and 95% CI was calculated for each association. Associations among independent variables were assessed using appropriate tests, such as x
2 or Fisher's exact tests, when indicated before performing logistic regression analysis. Multiple logistic regression models were used to examine the association between independent variables and the main outcome variable, HBV-seropositivity, while controlling for the effects of other covariates. All variables which were associated with outcome in bivariate analysis were included in the model. In logistic model, reference category (OR = 1) for OR estimate was HBV-negative participants. A probability of < 0.05 was considered as statistical significant. The final logistic regression model was obtained by forward selection based on single variables and their possible interactions. Given small number of hepatitis C infections, no tests of association could be performed.