Tests to determine the safety of blood products

There are about 700 blood donations a day in Finland. During each donation three tubes of blood are collected to carry out laboratory tests to determine the safety of blood products:

• One tube for blood typing
• Two tubes for infection screening
• Plus an additional tube from first-time donors to confirm their blood group.

Testing is carried out using tests designed specifically for blood donor examinations and which comply with Finnish legislation, FIMEA regulations and the EU Guide (EDQM).

Laboratory automation utilized in testing

Requests for tests on donor samples are generated at the time of blood donation and are automatically transferred from the blood donation information system to the laboratory information system as well as to the control systems of the automated track. The automated track combines the test requests and the donor samples sent during the evening and at night from blood donation sites to the laboratory in Vehkala.

The samples are transferred to the prehandler of the automated track where they are centrifuged, decapped and sorted. During prehandling, samples for blood typing are directed to their own sorting areas.

Samples for blood typing wait until morning to be processed, whereas the infection screening of samples begins right away at night utilizing automated serology and PCR testing integrated with the automated track.

The test results are ready by 1 p.m. the day after the donation and are transferred from the automated systems back to the blood donation information system and the blood product information system.

Blood typing tests

Each donated unit of blood is examined to detect:

• ABO and RhD blood groups
• Rh phenotype and
• K antigen

Samples given by first-time donors and by those who have been pregnant or received blood transfusions since their previous donation are screened for red blood cell antibodies. If red blood cell antibodies are detected and they are of clinical relevance, the products will be rejected. Clinically relevant antibodies are a permanent obstacle to blood donation.

A complete blood typing of red blood cells and plasma is performed for the first and second donations; with subsequent donations only red blood cells are used. Some donors are phenotyped and genotyped more extensively. The information systems compare the test results with any prior results for the donor in question. If the results are conflicting, the product is not released for patient treatment.

Infection screening

Serological infection screening is performed to detect the following:

• HIV (HIV Ag/Ab)
• Hepatitis B and C (HBsAg, HCV-Ab) and
• Syphilis antibodies

PCR testing is used to screen for the following:

• HIV, hepatitis B and C (HIV-RNA, HBV-DNA, HCV-RNA)
• Hepatitis A and parvovirus (HAV-RNA, B19-DNA)

The FINAS accreditation service has accredited most infection screening tests (test laboratory T119, accreditation requirement SFS-EN ISO/IEC 17025:2017, SFS-EN ISO 15189:2013). The hepatitis A and parvovirus tests have not been accredited.

All products that test positive in infection screening will be rejected. If a product tests positive, the donor will automatically be referred for additional examinations. Depending on the results of the additional screening and verification tests, the donor may be asked to provide a new sample. Based on the result of the re-examination the donor may be subject to a temporary or permanent donation disqualification.

Product release for patient treatment

Releasing a blood product for patient treatment requires that the blood typing and infection screening results are complete and acceptable. The infection screening results must be negative, i.e. there must be no signs of the pathogens tested for.

Product quality control testing

Statistical quality control tests are carried out on blood products to ensure that the blood product production process meets the quality requirements. Blood products are therefore randomly tested to determine values such as the following:

• haemoglobin level in red blood cell products
• thrombocyte count in platelet products
• residual leukocyte count in all leukocyte-free products to confirm the effectiveness of leukocyte filtration.

Products are also examined to ensure they have the necessary shelf life, and microbiological monitoring is carried out to prevent bacterial contamination.