REVIEW ARTICLES
HEPATITIS B INFECTION: WHAT THE PRIMARY CARE DOCTORS SHOULD KNOW
Loh Keng Yin MMed(FamMed UKM), Department of Family Medicine, International Medical University Kew Siang Tong FRCP(Lond), Department of Internal Medicine, International Medical University
Loh KY, Kew ST. Hepatitis B infection: what the primary care doctors should know. Malaysian Family Physician. 2006;1(1):8-10
EPIDEMIOLOGY
Hepatitis B infection is a global public health problem and causes significant morbidity and mortality. The worldwide prevalence of chronic hepatitis B infection is about 400 million people, and it causes 500 thousand deaths each year.1,2 The prevalence of chronic HBV infection is high (>8%) in certain part of Asia and Southeast Asia, including China, Korea, Indonesia, and the Philippines.1-3 In Malaysia about 1.1 million people are thought to be chronically infected with hepatitis B virus. The estimated prevalence of HBsAg among the population is approximately 4.7%. These data are obtained from Malaysian Liver Foundation in 1998.8
Hepatitis B infection is caused by the hepatitis B virus (HBV). The clinical manifestations of HBV infection (Figure 1) range in severity from asymptomatic subclinical infection (70%), symptomatic hepatitis (30%) to fulminant severe hepatitis with liver failure (0.10-0.5%).1,2 Following the exposure to HBV, up to about 10% of the patient will progress to chronic hepatitis B, which is defined as persistence of the infection for more than 6 months duration.5,6 The chronic hepatitis B then progress to liver cirrhosis and hepatocellular carcinoma in about 15-40% of the patients.1 The laboratory markers for hepatitis B infection and its interpretation are summarised in Table 1.
Table 1. Laboratory markers for HBV infection and its interpretation
| Marker* |
Interpretation |
| HBsAg | Exposure to Hepatitis B virus. Present in acute or chronic infection |
| Anti-HBs antibody | Immunity acquired via natural infection or immunisation |
| HBeAg | Marker of infectivity. It correlates with high level of viral replication |
| Anti-HBe antibody | It correlates with low level of viral replication |
| Anti-HBc IgM antibody | Infection in previous 6 months |
| Anti-HBc IgG antibody | Distant HBV infection or chronic HBV infection |
| Hep B DNA >105 copies /mL | Rapid viral replication |
*HBsAg Hepatitis B surface antigen, HBeAg Hepatitis B e antigen, Anti-HBc Anti-Hepatitis B core.
PREVENTION OF HEPATITIS B
In view of the magnitude and chronic complications, prevention of hepatitis B infection is paramount for the population in endemic regions and for those who are visiting endemic areas.
Health care workers, medical laboratory workers and blood bank staff who handle blood, blood products and body fluid must strictly adhere to standard precautions regulations so as to minimise unwanted accidental needle prick injury and direct contact with blood products. Screening of all blood products for blood transfusion has also been shown to reduce the risk of transfusion associated hepatitis B infection.1
HEPATITIS B VACCINATION
Among all the recommended strategies for preventing hepatitis B infection, vaccination is the most important one. Hepatitis B recombinant vaccine is available in most primary care clinics in Malaysia. The usual schedule of primary vaccination consists of three intramuscular doses of the vaccine. Universal neonatal vaccination against hepatitis B is effective and has been shown to favourably change the clinical course of hepatitis B infection especially in regions where this disease is endemic.7,8According to the Ministry of Health Malaysia childhood immunisation programme, all babies are given first dose of hepatitis B vaccine at birth; followed by 2nd dose at first month and 3rd dose at fifth month. This vaccine is very safe and has very few adverse effects. Common mild side effects are pain at the injection site (3%-29%) and elevated temperature >37.7°C (1%-6%).8 All adults who are at high risk of infection such as health care workers, blood bank staffs, public health workers, patients who require multiple transfusion or blood products, haemodialysis patients, homosexual men and intravenous drug users must be vaccinated. Testing for hepatitis B surface antibody titre should be done 6-8 weeks after the last dose.8 The protection following vaccination lasts 10-15 years. After 15 years from the last vaccination, it is advisable to get a booster dose. Those with chronic renal failure, immunosuppressed patient, haemodialysis patients and elderly may have a lower response rates.6,7