Best tests October 2009
QUIZ FEEDBACK: Hepatitis
Full colour PDF of the pages as they appeared in ‘best tests’.
This quiz provides an opportunity to revisit the recent bpac “best tests” that had a key focus on hepatitis testing.
The resource provided an overview of testing for hepatitis infections, including an overview of risk factors. A number of scenarios were discussed, particularly including pre- and post-immunisation situations, that a GP may be faced with in their day-to-day practice.
A key message that came through strongly from the quiz feedback is the importance of considering a number of factors when ordering hepatitis tests. It is important to think about patient’s history, age, risk factors, vaccination status and any previous hepatitis test results.
The quiz feedback includes the aggregated responses from GPs that completed the quiz, comments from the GP review group and specialist commentary from Dr Susan Taylor.
All GPs who responded to this quiz receive CME points. There are now in excess of 25 interactive quizzes available which provide an ongoing opportunity for accumulating CME points. These are available from www.bpac.org.nz.
|1. Risk factors for hepatitis A include:||Your peers||GP Panel|
|Men that have sex with men||97%|
|IV drug user||90%|
|Infants born to infected mothers||12%|
|Previous blood transfusion||2%|
It is clear that most people are aware which of the above are risk factors for hepatitis A. The panel was curious as to why IV drug use is a risk factor, when it is known transmission of hepatitis A is by the faecal-oral route. It was suggested there may be increased risk because the living conditions for many IV drug users may be substandard (with overcrowding and poor personal hygiene) and associated with increased exposure to faecal contamination. Perinatal transmission of hepatitis A is rare. If the mother develops symptoms two weeks before to one week after delivery, the infant may be given IG (0.02 mL/kg), although its efficacy in these circumstances has not been established.
The most common reported source of infection is household or other close contact with an infected person. Outbreaks of hepatitis A infection among injecting drug users have been reported in North America and Scandinavia. Several routes of transmission are likely to occur including a combination of person-to-person and percutaneous spread. Poor personal hygiene among drug users may be a source of hepatitis A contamination of drugs or drug paraphernalia, as well as direct person-to-person transmission. Viraemia occurs within 1–2 weeks after hepatitis A exposure and persists through the period of liver enzyme elevation. Virus concentration in serum is 2–3 log10 units lower than in stool. Percutaneous transmission of hepatitis A by needle sharing can occur. Faecal contamination of drugs by rectal transportation has been reported but is probably a rare source of infection.
|2. Risk factors for hepatitis B include:||Your peers||GP Panel|
|Men that have sex with men||99%|
|IV drug user||100%|
|Infants born to infected mothers||99%|
|Previous blood transfusion||33%||+/-|
Again, these responses demonstrate that GPs are very clear about risk factors for hepatitis B infection.
There were mixed responses to whether a blood transfusion is a risk factor of hepatitis B. It was acknowledged that some people would be chronically infected from receiving infected blood prior to routine blood screening in New Zealand. Following the implementation of blood screening for hepatitis B in New Zealand in 1971, the risk of contracting hepatitis B through a blood transfusion in New Zealand, is now considered extremely low.
In the United States, the risk of post-transfusion hepatitis B is estimated to be one to four per million blood component transfused. In endemic countries the risk may be higher, although nucleic acid testing aims to reduce this and has been introduced in some countries.
|3. Risk factors for hepatitis C include:||Your peers||GP Panel|
|Men that have sex with men||18%|
|IV drug user||100%|
|Infants born to infected mothers||84%|
|Previous blood transfusion||94%|
The panel discussed the uncertainty that currently exists about how infective Hepatitis C is, particularly in relation to sexual activity. The panel commented they had known of situations when an individual had hepatitis C, but their sexual partner had continued to remain negative for many years.
This led on to a discussion about the likelihood of an increased theoretical risk of transmission from a newly infected person who hadn’t yet developed symptoms, ie still in the ‘window period’.
Successful antiviral therapy may remove the possibility of transmission to partners. Sexual transmission of hepatitis C occurs at a low rate (<1% per year of relationship or about 2% of partners in long-term relationships). These rates increase if the index case is also HIV infected.
Most patients (>60%) do not have symptomatic acute infection. This means many infections are only detected by screening asymptomatic patients at increased risk of infection. HCV RNA is detectable about 2 weeks after infection whereas the appearance of anti-HCV takes 8–9 weeks. For the minority who experience symptoms, these occur around 6–8 weeks after infection.
Vertical (mother to infant) spread also occurs at a low rate (2– 5%). Higher rates are seen if there is HIV co-infection.
|4. What best describes chronic hepatitis A infection?||Your peers||GP Panel|
|40–50% of children aged 6-14 will go on to develop chronic hepatitis A||1%|
|Only people who develop jaundice go onto to develop chronic hepatitis A||0%|
|Chronic hepatitis A only develops in immunocompromised people||1%|
|Hepatitis A does not develop into a chronic hepatitis||99%|
It was clear from the responses that GPs are very aware that Hepatitis A does not develop into a chronic hepatitis. This lead on to a discussion, as to whether there are any long term health issues as a result of hepatitis A.
Hepatitis A is rarely complicated by extrahepatic manifestations or fulminant hepatitis. However, the expectation is that patients will recover without sequelae.
|5. Post vaccination immunity check for hepatitis B is indicated for:||Your peers||GP Panel|
|High risk occupational or exposure groups||90%|
|5 month old babies born to Hepatitis B surface antigen positive mothers||91%|
|All children in areas with high prevalence of hepatitis B||4%|
|People requiring reassurance the vaccine has “worked”||9%|
The panel discussed the scenario of the patient who requests confirmation/reassurance that the vaccine “has worked”. They agreed that it would be a situation to discuss the current recommendations that post vaccination immunity check for hepatitis B is not routinely indicated. However ultimately the patient makes an informed choice.
The panel found it helpful to be reminded of the practice in NZ whereby pregnant women are offered a blood test to see if they are chronic carriers of hepatitis B. Babies born to infectious mothers are immunised soon after birth with Hepatitis B vaccine and immunoglobulin, then receive the national immunisation schedule vaccines at the usual times. At 5 months a blood test is taken to check for seroconversion/antibody levels. If the anti-HBs measurement is less than 10 mIU/mL the baby should be given further doses of vaccine at 6 & 7 months with a repeat blood test at 8 months of age.
Infants born to hepatitis B infected mothers should be tested at around 5 months for both HBsAg and anti-HBs. In addition to measuring antibody response to vaccine, this is to identify the approx 5% of infants that are hepatitis B infected (and therefore will likely have chronic infection) despite immunoprophylaxis. With appropriate immunoprophylaxis, breast-feeding of infants poses no additional risk for the transmission of hepatitis B.
|6. What tests would be indicated for a person with a clinical presentation of acute hepatitis, with a history of recent overseas travel?||Your peers||GP Panel|
|Hepatitis A IgG antibody||7%|
|Hepatitis A IgM antibody||97%|
|Hepatitis B surface antibody||7%|
|Hepatitis B surface antigen||76%|
|Hepatitis B core IgM antibody||64%|
|Hepatitis C antibody||21%||+/-|
The panel were in agreement about the tests to be done to help diagnose the cause of an acute hepatitis but voiced that it might tempting to order a Hepatitis C antibody test for completeness sake even if someone was not a drug user. Although it is worth remembering that the majority of patients with newly acquired hepatitis C will be asymptomatic.
While it is preferable to carefully choose the tests based on the clinical scenario, this can be difficult in practice. In addition the combination of tests is often predefined in the PMS system or on the laboratory form. It is useful to provide clinical details on the laboratory requisition form, as this can help the laboratory with appropriate test choices.
No further comment
|7. Which is true about pre-immunisation screening for hepatitis B||Your peers||GP Panel|
|Is only indicated for those at higher risk of being a carrier of hepatitis B||88%|
|People at low risk of hepatitis B may be vaccinated without prior screening||75%|
|Only people travelling to high risk areas should have pre-immunisation screening for hepatitis B||4%|
|People that may have been exposed to hepatitis B as a child should be screened prior to immunisation||36%|
The panel were in agreement that pre-immunisation screening is indicated for those at higher risk of being a hepatitis B carrier. They acknowledged this may include those infected as a child, since approximately 90% of infected infants and 25–50% of infected children aged 1-5 years will remain chronically infected.
The panel were unsure what the risks would be if an immune person or hepatitis B carrier was inadvertently vaccinated for hepatitis B. They were also interested about what further vaccinations were required for someone who had started or partially completed a hepatitis B vaccination course but never finished it.
The role of pre-vaccination screening is to identify individuals who do not require vaccination and to reduce unnecessary vaccination. The need for pre-vaccination screening should be guided by the likelihood that an individual has been exposed to hepatitis B. For high risk groups, this may be an opportunity to identify a chronically infected patient who may benefit from ongoing surveillance and treatment. The administration of hepatitis B vaccine to individuals who are infected or immune will not result in any adverse outcome.
Longer than recommended intervals between doses do not reduce final antibody concentrations. An interruption in the vaccination schedule does not require restarting the entire series of vaccination or adding extra doses. If the vaccination series is interrupted after the first dose, the second dose should be administered as soon as possible. The second and third doses should be separated by an interval of at least two months. If only the third dose is delayed, it should be administered when convenient.
|8. A patient has requested vaccination for hepatitis A prior to travel to Indonesia. What laboratory testing is indicated?||Your peers||GP Panel|
|Pre-immunisation screening is not usually recommended||91%|
|Both Hepatitis A IgG antibody and Hepatitis A IgM antibody||1%|
|Hepatitis A IgG antibody||24%|
|Hepatitis A IgM antibody||1%|
The panel agreed that for the vast majority of people travelling to a country with high risk of hepatitis A vaccination without prior screening was indicated. In this scenario the panel advocated use of a hepatitis A vaccine (sometimes used in combination with other vaccines such as Hepatyrix or Twinrix) and then another booster within 6 months if the patient wants to maximize duration of future cover.
Agree, most people do not require pre-travel screening.
Pre-vaccination antibody screening (Hepatitis A IgG antibody) is only justified in older travellers, those who have lived in areas where hepatitis A is endemic (average prevalence of immunity of over 30 percent), or those with a history of jaundice.
GP Review Panel:
- Dr Janine Bailey, Motueka
- Dr Suzie Lawless, Dunedin
- Dr Neil Whittaker, Nelson
- Dr Marie Neylon, Dunedin
- Dr Susan Taylor, Clinical Microbiologist , Diagnostic Medlab, Auckland
bpacnz would like to thank the GP review panel and Dr Susan Taylor for their expertise and guidance on the development of this quiz feedback.
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