Serological tests
The screening tests carried out in the biological qualification of the donation (QBD) laboratories include serological tests (search for specific antibodies directed against an infectious agent or search for antigen) and tests for the detection of viral genomes (DGV).
The regulations provide for systematic screening, on each blood donation, of biological markers of viral infections caused by HIV (anti-HIV 1, anti-HIV-2 and DGV HIV-1 antibodies), HTLV I-II (anti-HIV -HTLV-I, anti-HTLV-II), hepatitis B virus (anti-HBc antibodies, HBs antigen and DGV HBV) and hepatitis C virus (anti-HCV and DGV HCV antibodies).
The causative agent of syphilis (Treponema pallidum) is also screened on each donation by a serological test (TPHA). A donation is compliant when all the screening tests are negative.
Complementary analyzes
This screening can be supplemented according to the risk factors sought during the pre-donation interview (concept of travel, and other risks), by the search for antibodies directed against the parasites responsible for malaria (Plasmodium species) and/or other diseases such as Chagas (Trypanosoma cruzi).
In addition to the blood tests provided for by the regulations, the Blood Transfusion and Treatment Establishment can choose to carry out other screenings, such as anti-HLA antibodies in women participating in therapeutic plasma donation or platelet donation by apheresis, and having had at least one child. In addition to the postponement of people with a history of transfusion, this measure aims to reduce the risk of occurrence of TRALI (Transfusion Related Acute Lung Injury) with blood products from these donations.
For the Fractionation and Biotechnology Laboratory (LFB), which manufactures medicines and therapeutic products derived from blood, research on anti-tetanus and/or anti-HBs antibodies can be carried out on plasma donations.
Specific analyzes as needed for the manufacture of specific products (HEV) or to further secure blood products in the event of an epidemiological risk can also be carried out.
Limitations of serological tests
Serological tests have detection limits, known as the "serological window". This serological window, which lasts a few days, is due to the delay in the appearance of antibodies in the human body, following contact with the pathogenic agent.
In addition, some donors may not produce antibodies following an infection (non-responders or sero-negative), and present a variant microorganism which will not be detected by the tests.
