Testing of donated blood
The first step in reducing the risk of transmission of infectious diseases through blood is to select voluntary non-remunerated donors from low-risk populations who give blood on a regular basis as these individuals are at a lower risk of transmitting transfusion-transmissible infections than are family/replacement donors, or paid donors. However, even with the most careful selection, some donors may be seropositive for HIV or other infectious agents. Therefore, rigorous screening of all donated blood is required to ensure the safety of the blood supply.
Unfortunately, not all donations in all countries are screened. GDBS data from 1998–1999 indicated that, globally, 13 million tests were not performed for HIV, hepatitis B (HBV), hepatitis C (HCV) and syphilis. Data for 2000–2001 indicate an improvement in the number of tests performed for these markers, largely because a number of countries had introduced testing for HCV since the previous collection of data. Nevertheless, more than 6 million tests were not performed on donated blood for either HIV, HBV, HCV and syphilis. The donated blood should also be tested for ABO and RhD to ensure the safety and compatibility of the transfusion for the patient.
In order to ensure safety of the blood supply, several key activities must be implemented:
- the development and implementation of a national strategy for the screening of all donated blood for transfusion-transmissible infections, using the most appropriate and effective assays to test for HIV, hepatitis viruses, syphilis and other infectious agents, such as Chagas disease;
- the training of blood transfusion service laboratory technical staff in all aspects of blood screening and processing including blood grouping, compatibility testing, component preparation and storage and transportation of blood products;
- Maintenance of quality assurance systems and good laboratory practice, including the use of standard operating procedures, in all aspects of blood screening and processing;
- Compatibility testing of all whole blood and red cells with the patient to be transfused must always be performed even if, in life-threatening emergencies, this is done after the transfusion has been completed;
- The procurement, supply, central storage and distribution of reagents and materials to ensure continuity in testing at all sites;
- The maintenance of an effective blood cold chain for the storage and transportation of blood and blood products.
WHO encourages and supports countries, through provision of advice and training, in the development and implementation of these activities in accordance with their needs. Guidelines, recommendations and reports on testing strategies and appropriate test kit selection have been developed, a bulk procurement scheme for HIV test kits has been established, and external quality assurance programmes are being carried out in several regions. The EHT Diagnostics laboratory section covers these and other aspects of blood screening in more detail.