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Annual review of infections in UK blood, tissue and organ donors
PHE has published the joint NHS Blood and Transplant/PHE Epidemiology Unit’s annual review, ‘Safe Supplies: a Year of Change’, which highlights major changes in donor selection criteria and testing policies, summarises key findings from the blood, tissue, cell and organ surveillance programmes during 2017, and emphasises the safety of the supplies .
A combination of donor selection and donation testing is used by the UK’s blood services to maintain safety. SaBTO, the DHSC expert committee on the safety of blood, tissues and organs, may be asked to review and make recommendations about donor selection policy. Following a recent review of donor selection policies related to sexual behaviours, people who inject drugs and piercing events such as tattoos and body piercings, SaBTO made a number of recommendations to government . This resulted in the English, Welsh and Scottish blood services, in November 2017, changing their donor selection criteria for three categories of donor – those with partners who may be at increased risk of acquiring a blood-borne infection; men who have sex with men; and commercial sex workers – from a 12 to 3 month deferral since last sex. Recommendations were also made relating to piercing events and injecting drug use but could not be implemented because of the current laws covering blood donations.
Testing of donated blood
In 2017 there were 2 major changes to the way in which donations were tested. In previous years all donations were tested for the presence of HTLV whereas, from February, NHSBT tested only donations from new blood donors and donations which were issued as granulocytes. Another major change was the move from testing at least 30% of donations for hepatitis E virus (HEV) to universal testing, with all blood components now issued as screen negative for HEV.
Markers of infection in donated blood: viral infections
Among almost 2 million whole blood and platelet donations made by around 1 million donors in the UK in 2017, only 179 were positive for the mandatory markers of infection and thus removed from the supply. This represents a very low rate of positivity – one in 10,000 donations – with markers of hepatitis B and syphilis the most common. Generally, positive donors had previously undiagnosed chronic infections, only four viral infections (1 HIV and 3 HBV) were likely to have been acquired within 12 months, suggesting donor selection is very effective at identifying low risk individuals. The risk that testing could miss a positive donor remains extremely low, with undetected HBV, HCV and HIV infections estimated at less than 1 in 2 million donations.
Markers of infection in donated blood: bacterial infections
Bacterial screening of platelets is in place across all UK blood services with detection rates remaining relatively constant year-on-year. Among both apheresis and pooled platelets screened in 2017, the confirmed positive rate for each UK blood service was less than <0.1%. Most bacteria identified on screening originated from the skin, with Propionibacteria being the most frequently identified. This species would not usually cause a clinical reaction; however, some species with potential to harm donors and recipients have been detected and removed from the supply. Bacterial safety measures do not completely remove the risk of a positive unit being released so vigilance remains important.
Transfusion-transmitted infections continue to be extremely rare. In 2017, among 114 incidents investigated by the blood services, only 2 were confirmed: one hepatitis A infection associated with a platelet transfusion linked to the ongoing hepatitis A outbreak in the general population; and an HEV transmission associated with a pooled platelet transfusion when selective screening was in place – a donation that had not been screened.
In recent years there has been a decrease in the number of living donors donating bone, due to good stock levels. In 2017, 2 donors tested positive: one HCV and one syphilis positive. Deceased donors have the highest rates of positivity which may reflect their age: six were positive for syphilis and seven for HBV. During 2017 no cord blood donors tested positive. Antenatal screening will select out women positive for HBV, HIV and syphilis.
The UK has a robust process in place for the review of current and future infectious risks to blood safety. This is mainly in the context of blood donation but may have implications for tissue and organ donation too. The unit works closely with colleagues in PHE and wider blood services across the world; data collected contribute to risk assessments and may result in additional tests or changes to donor selection criteria being implemented eg the spread of Chikungunya in Italy resulting in a donor deferral being implemented.
Further information about the data held by NHSBT is available on request from email@example.com.
PHE website (July 2018). Safe Supplies: a Year of Change.
PHE website (July 2017). Donor Selection Criteria Report (2017).