A case-control study of risk factors for acute Hepatitis B virus infection in Karachi

Date of Award


Document Type


Degree Name

Master of Science in Epidemiology & Biostatistics (MSc Epidemiology & Biostats)


Community Health Sciences


Hepatitis B virus (HBV) infection is a major public health problem in developing countries including Pakistan. HBV infection may lead to chronic HBsAg carrier state in the majority of infants and a smaller proportion of adults. These chronic carriers go on to develop chronic liver disease and hepatocellular carcinoma with extremely poor prognosis. For a better control of HBV infection, universal hepatitis B vaccination program for under five children, which is being instituted in Pakistan needs to be supplemented with interventions targeted at risk factors for HBV transmission. Therefore a case control study was conducted to identify the risk factors for acute HBV infection among patients coming to major tertiary care hospitals of Karachi, Pakistan. We enrolled 67 cases of acute hepatitis B virus infection (IgM HBc positive) and 24'7 controls (total anti-HBc negative) tested by enzyme capture immunoassay (EIA) from four tertiary care hospitals of Karachi during July I7th, 2000 to June 30th, 2001. A structured questionnaire was administered to collect history of exposure to various risk factors during last 6 weeks to 6 months prior to the onset of illness for cases and from the time of interview for controls along with socio-demographic information. The mean age of ca.ses and controls was 29 and, 27 years respectively. Among cases, 67% (45/67) were males compared to 58% (143/247) among controls. In multivariate analysis, cases as compared to controls were more likely to receive one injection (OR = 4.0; 95% CI: 1.4, 11.1), or more than one injection (OR =6.3; 95% CI: 3.2, 12.4) while adjusting for age, gender, ethnicity, number of household members, and enrollment hospital. The estimated population attributable risk percent for therapeutic injection was 53% (95% CI: 40% to 58%). Also the cases were more likely to have household size of 7 or more people (OR = 1.9; 95% CI: 0.95, 3.9) as compared to controls, taking l-6 persons in a household as reference category. Further more, cases compared to controls were more likely to be Pathans (OR =2.5; 95% CI: 1.1, 5.8), Sindhi (OR = 5.4; 95% CI: 1.7, 18.0), or Hindko (OR = 3.7: 95% CI: 0.97, 14.0) than Urdu. Other exposures including intravenous drips, hospitalization, blood transfusion, dental treatment, personnel handling blood/syringes, tattooing, and intravenous drug use were not frequent enough in the case series to show statistically and intravenous drug use were not frequent enough in the case significant association with acute HBV infection' The results suggest that therapeutic injections are the major risk factor for HBV infection in Karachi, Pakistan. We recommend interventions to discourage the use of unnecessary injections. Further research is needed to estimate the proportion of unnecessary injections and the economic burden it imparts on health system' We also recommend research to identify factors for horizontal transmission of HBV infection.

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