Monday July 28 2014
Researchers screened blood donations for the hepatitis E virus
"One in almost every 3,000 blood donors in England could be infected with hepatitis E, according to a new study," The Times reports.
Hepatitis E normally causes only a mild infection that usually clears up without the need for treatment. It can occasionally lead to more serious complications in more vulnerable groups, such as pregnant women and people with a weakened immune system.
A new study estimated the prevalence of hepatitis E virus in blood donors in England and whether the virus is transmitted to blood recipients.
The prevalence estimate, based on just under a quarter of a million blood donations, was found to be one infection in every 2,848 donors (0.04%). This was higher than expected.
When researchers investigated what happened to 49 of the 60 people receiving the infected blood, they found it did not cause significant illness and recipients were able to clear the virus from their bodies naturally in most cases.
This opens up debate about whether screening donated blood for hepatitis E is necessary to prevent infections – currently only the B and C types of hepatitis are screened for.
In an ideal world, blood donations would be screened for all known blood-borne organisms. But in the real world, screening is expensive and time consuming, and is often not accurate enough to be useful.
The rationale for not screening is because hepatitis E infections are generally considered a mild and short-term infection, unlike the other forms of hepatitis, which are screened for.
The current study does not resolve this screening debate, but it does provide useful new information to inform it.
Where did the story come from?
The study was led by researchers from NHS Blood and Transplant in the UK, and was jointly funded by Public Health England and NHS Blood and Transplant.
It was published in the peer-reviewed medical journal The Lancet.
Both The Times' and BBC News' coverage was broadly accurate and provided useful expert opinions for and against screening donated blood for hepatitis E.
What kind of research was this?
This was a cross-sectional study looking at historically donated blood to see:
- how many samples were infected with hepatitis E virus
- whether these samples were given to other people
- if so, what happened to these people
Hepatitis E is an infection caused by the hepatitis E virus and is generally considered a mild and short-term infection that often goes away on its own. However, in pregnant women and people with a compromised immune system it can cause serious liver disease, which can be fatal.
It is caught by putting something in your mouth that has been contaminated with the faeces of someone with hepatitis E, eating contaminated food such as processed pork, or through infected blood donations.
The study authors indicate the prevalence of hepatitis E virus (specifically, genotype 3) infection in the English population, including blood donors, is unknown, but is probably widespread. They say the virus has been detected in donated blood products previously.
To investigate these unknowns, the researchers looked at around a quarter of a million English blood donations to find out the prevalence of hepatitis E virus in the donations.
What did the research involve?
From October 2012 to September 2013, the researchers retrospectively screened 225,000 blood donations collected in southeast England for hepatitis E virus genetic material as evidence for viral contamination. Donations containing hepatitis E virus were further investigated in the laboratory.
Recipients who received any blood components from these donations were identified and the outcome of exposure to the virus was ascertained.
They were identified and recruited using records from the NHS Blood and Transplant service, hospital transfusion teams, and GPs.
Blood samples of recipients that could be contacted were collected and analysed for signs of past and current infection.
What were the basic results?
From 225,000 individual donations, 79 donors were found to have hepatitis E, a prevalence of one in 2,848.
Most donors with hepatitis E were seronegative at the time of donation, meaning their body was not producing antibodies to fight the virus at the time of donation.
The 79 donations had been used to prepare 129 blood components. These were used to give blood components to 60 recipients before identification of the infected donation.
Of the 60 recipients, one declined to take part in the study and 16 were not available for follow-up, nine had died, five were terminally ill and therefore considered inappropriate to start hepatitis E monitoring, and two had left the country.
Hepatitis E was not judged by the clinical team to have contributed to illness or death in any of these cases.
Follow-up of the remaining 43 recipients showed 18 had evidence of infection. Absence of detectable antibody and high viral load in the donation made infection more likely.
Follow-up of the infected recipients showed a varied response to infection, reflecting their overall medical condition and inferred strength of their immune systems.
Recipient immunosuppression (weakening of the immune system) delays or prevents the body producing antibodies to fight the virus, and extends the duration the virus stays and replicates in the body.
Spontaneous clearance of the virus without disease was common and resulting acute illness was rare.
Three recipients cleared longstanding infection after intervention with the antiviral drug ribavirin or through alteration in immunosuppressive therapy.
Ten recipients developed prolonged or persistent infection.
Transaminitis (high levels of liver enzymes, indicating inflammation and possible liver damage) was common, but short-term illness was rare. Only one recipient developed apparent but clinically mild post-transfusion hepatitis.
How did the researchers interpret the results?
The team concluded that, "Our findings suggest that HEV genotype 3 infections are widespread in the English population and in blood donors. Transfusion-transmitted infections rarely caused acute morbidity, but in some immunosuppressed patients became persistent.
"Although at present blood donations are not screened, an agreed policy is needed for the identification of patients with persistent HEV infection, irrespective of origin, so that they can be offered antiviral therapy."
They added: "On a clinical basis alone, the resulting minimal burden of disease does not signal a pressing need for donation screening at this time."
This study estimated the prevalence of hepatitis E virus in blood donors and found a higher than expected figure of around one infection in every 2,848 donors.
They found the infection was passed to the recipient of the blood in some cases, but this did not cause significant illness and recipients were able to clear the virus from their bodies naturally in most cases.
This study, which coincides with World Hepatitis Day, increases our awareness that the prevalence of hepatitis E in England might be higher than previously assumed.
A second issue stemming from the study is whether, given the higher than expected prevalence, it is necessary to screen donated blood for hepatitis E to prevent infections – something that is not currently done.
Although most infections are mild and heal themselves, there is the potential for far more serious effects if infected donations are given to immunocompromised people or pregnant women.
The BBC interviewed Professor Richard Tedder of Public Health England, who said there was no immediate need to screen donated blood.
This view was not shared by Professor Jean-Michel Pawlotsky of the Université Paris-Est, who said this stance was "surprising" and that he believed "systematic screening of blood components for markers of hepatitis E infection should be implemented".
Another practical consideration is that screening for hepatitis E costs money that could be spent on other health areas.
Would spending money to prevent the spread of a usually mild infection be a prudent use of healthcare resources? Would the money be better spent elsewhere? These are the sorts of questions healthcare systems around the world have to consider regularly.
They base their decisions on the best available evidence and the balance of risks and benefits in their populations. There are no easy answers and debates following new evidence are a healthy part of this dialogue.
Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter. Join the Healthy Evidence forum.