Screening blood donors for infection (note)
drsuryabrata@gmail.comPlease note this is a study note, keeping the exam in mind. This is not a guideline and should not be used for that purpose. It is not for clinical use either. You should contact your doctor for clinical advice.
Blood donation screening
| ORGANISM | MANDATORY TEST | ADDITIONAL TEST |
|---|---|---|
| HIV | anti-HIV 1+2 or HIV 1+2 Ag/Ab | HIV RNA* |
| Hepatitis B | HBsAg | 1. HBV DNA* 2. anti-HBc [+ anti-HBs] |
| Hepatitis C | 1. anti-HCV 2. HCV RNA | |
| Syphilis | anti-treponemal Ab | |
| HTLV I/II | Anti-HTLV I/II: anti-HTLV screening is only required for blood donations from previously untested donors and for blood donations destined for use to prepare non-leucodepleted products | |
| Hepatitis E | HEV RNA | |
| CMV | CMV IgG +/- IgM (Ideally both, but IgG is sufficient) | |
| Malaria | anti-P. falciparum/vivax | |
| Trypanosoma cruzi | anti-T. cruz | |
| West Nile Virus | WNV RNA |
*Although neither is mandatory for blood donations in most of the UK, HIV RNA and HBV DNA are included in the nucleic acid amplification techniques (NAT) screen as the commercial systems available are now triplex assays. HIV RNA is mandated within Scotland.
Additional tests due to specifically identifiable risk, for example, malaria testing if the donor has recently travelled to a country where malaria is endemic.
Residual risk
The viral residual risk for UK blood donations is defined as the risk that a potentially infectious donation is not detected by routine blood donation screening and could potentially be available for transfusion. It is mainly due to the test being done within the window period. Residual risk is only calculated for HBV, HCV and HIV.
| VIRUS | ASSUMED ALL DONATIONS WERE TESTED FOR | WINDOW PERIOD | ESTIMATED RESIDUAL RISK (AND 95% CONFIDENCE INTERVAL) THAT A DONATION MADE INFECTIOUS WINDOW PERIOD IS NOT DETECTED ON TESTING: UK, 2018-2020 (ALL DONOR TYPES) |
|---|---|---|---|
| Hepatitis B | HBsAg and HBV DNA using NAT | 30 days | 0.81 |
| Hepatitis C | Anti-HCV testing and HCV RNA testing | 4 days | 0.02 |
| HIV | Combined HIV antigen/antibody testing and HIV NAT | 9 days | 0.04 |
Reference: Joint UKBTS Professional Advisory Committee – The estimated residual risk that a donation made in the infectious window period is not detected on testing: risks specific for HBV, HCV and HIV in the UK (2021)
The minimum level of sensitivity for screening
| HBsAg | 0.2 IU/mL. |
| HIV 1+2 serological screening, Anti-HCV, HTLV I/II | a positive result should be obtained with the UK working standard available from NIBSC. |
| the minimum sensitivity level for HCV NAT's performance is 5000 IU/mL in an individual donation. | Anti-HBs, anti-HBc Syphilis, CMV, and Malaria |
| HCV RNA PCR | Currently, no specific UK requirement for the minimum level of sensitivity |
| HBV DNA PCR, HIV RNA PCR, HEV RNA PCR, WNV PCR | Currently no specific UK requirement for the minimum level of sensitivity |
| T cruzi | a positive result should be obtained with a formally validated in-house anti-T. cruzi quality control preparation. |
- Donations found to be reactive for anti-HBc with levels of anti-HBs <100 mIU/mL are deemed unsuitable for release, whereas those with levels >100 mIU/mL can be considered suitable for release.
Any possible incident of infection –
should be reported by the hospital where the transfusion took place to the local blood centre.
Each case reported is fully investigated to identify the infection and to confirm or refute that the blood transfusion may have been the source of the infection.
After the investigations are closed, reported incidents are classified as transfusion-transmitted infections (TTI).
Tissue and stem cell donation screening
| ORGANISM | MANDATORY TEST | ADDITIONAL/OPTIONAL TESTS |
|---|---|---|
| HIV | Anti-HIV 1+2 or HIV 1+2 Ag/Ab | HIV RNA (optional) |
| HBV | 1. HBsAg 2. Anti-HBc [+ anti-HBs] | HBV DNA (optional) HBV DNA screening should be on individual samples; not as pooled samples. |
| HCV | Anti-HCV | 1. HCV Ag and/or HCV Ag/Ab (Optional) 2. HCV RNA (optional) |
| Syphilis | anti-treponemal Ab | |
| HTLV I/II | anti-HTLV I/II Not mandatory for avascular tissue donations but may be considered good practice. | |
| CMV | CMV antibodies (Additional) | |
| Malaria | anti-P. falciparum/vivax (Additional) | |
| Trypanosoma cruzi | anti-T. cruzi (Additonal) | |
| West Nile Virus | WNV RNA (Additional) |
Orange – the difference with blood screening
All screening of deceased tissue donations is performed on individual samples. HCV and HIV RNA and anti-HTLV I/II screening of surgical tissues/stem cells can be performed using pools of a maximum of 24 samples.
Optional – optional genomic screening for HIV, HCV and HBV is not mandated but can be performed on the original donation sample as an alternative to 180 days’ quarantine and follow-up serological testing.
Additional – additional due to specifically identifiable risk, Other tests, e.g. Epstein-Barr virus, toxoplasmosis, may be required as additional tests depending upon specific additional risk and/or special requests for individual recipients. For certain product types that are exported, there may be additional end-user testing requirements.
Reference
- https://www.transfusionguidelines.org/red-book/chapter-9-microbiology-tests-for-donors-and-donations-general-specifications-for-laboratory-test-procedures
- https://www.transfusionguidelines.org/document-library/position-statements
- https://www.gov.uk/guidance/blood-tissue-and-organ-donors-surveillance-schemes
- Emerging infection: https://www.gov.uk/guidance/emerging-infections-horizon-scanning
- https://www.gov.uk/government/collections/bloodborne-infections-in-blood-and-tissue-donors-bibd-guidance-data-and-analysis
- https://www.who.int/bloodsafety/ScreeningTTI.pdf
