Estimated Frequency Infectious Donations entering the UK blood supply

Although current blood donation testing strategies minimise the risk of transfusion transmitted infections in the UK, on very rare occasions infectious donations are not detected and enter the blood supply. This is mostly because a blood donation is made during the infectious 'window period' (WP) early in the course of infection when the test in use will not detect the marker of infection. The risk due to the WP is estimated here. It is also possible that a false negative test result may arise because of issues relating to assay sensitivity other than WP, or a blood donation may be erroneously issued as negative due to sampling/processing/issuing error. The contribution of these latter two elements to the overall risk is likely to be very small and has not been estimated this year because of uncertainty around these values.

Based on these estimates, assuming 2.5 million donations per year, we would expect testing not to detect two HBV infectious donations every year, one HCV every 29 years, one HIV every two to three years, and one HTLV-1 every three years. There has not been a confirmed transfusion transmitted infection since 2005, however, this is a passive surveillance system and may be biased as a result of infections either not being attributed to transfusion, or transfusion recipients dying before an infection became evident.

For further information, please see our 2010 annual review entitled 'Safe supplies: Focusing on epidemiology'

Last reviewed: 4 October 2011