HBV is present in high titres in the blood of infected patients and in moderate quantities in saliva, semen and vaginal secretions. The three principle modes of transmission are through blood (needle-sharing), sexual activity and mother-to-infant. In adults only approximately 30% of acute infections result in jaundice and many cases go undiagnosed. About 5% of adults infected with hepatitis B become chronic carriers, and amongst these those who are positive for hepatitis B e-antigen are the most infectious. Approximately 20% of these carriers will go on to develop progressive liver disease which in some cases will lead to cirrhosis and hepatocellular carcinoma.
TESTING
Carriers are diagnosed by the presence of hepatitis B s-antigen. The presence of hepatitis B s-antibody may indicate either current infection, resolved infection or successful immunisation. (See appendix 6, page 122 for test result interpretations). Pre- and post-test counselling, as described above under HIV testing, should occur before testing.
All injecting drug misusers who are not already immune (hepatitis B s-antibody negative) should be offered vaccination; this offer should extend to the close household contacts (especially sexual contacts) of those who are currently infected (hepatitis B s-antigen positive). Bearing in mind compliance, full protection is more likely to be achieved with use of newer formulations which can be administered over a period of weeks rather than the usual 6 months. A typical schedule involves administration of 'Engerix B' at 0, 7 and 21 days with testing 6 to 8 weeks after the third dose (Bock et al, 1995). If the patient has demonstrable antibodies after three doses they probably do not require a booster at 12 months. If the patient has not responded to the three dose course testing should take place for full hepatitis B markers, as the most likely cause of non-responsiveness is being a carrier of the hepatitis B virus. Testing with oral swabs has recently become available but has yet to be fully evaluated.
Current and past injecting drug misusers who are infected (hepatitis B s-antigen positive) should be referred to a specialist with expertise in liver disease for further assessment. Therapy for chronic hepatitis B infections is available, but is expensive and not generally employed. Interferon alpha subcutaneously three times per week decreases HBV replication (Wong,Yim et al, 1995). Post-exposure prophylaxis with hepatitis B immunoglobulin (HBIG) (followed by vaccination) is recommended for perinatal, percutaneous, ocular, mucous membrane and sexual contacts.
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The above information is copyright of Dr Bruce Trathen MBBS MRCPsych (2006). ISBN 0-9545164-0-0. The author grants permission for these guidelines to be downloaded, copied and distributed freely, but does not grant permission for their sale.
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