Transfusion transmissible infections are the special category of infections which can transmit through the transfusion of blood or blood components.
These microbial agents can cause morbidity and mortality in recipients. Therefore it is very important to do the screening tests to identify these infections before transfusion. So it is the responsibility of the government to assure a safe and sufficient supply of blood for all patients.
This procedure involves a number of processes.
- Selection of blood donors.
- Collection processing.
- Testing of blood donations.
What is the screening of Transfusion Transmissible Infections?
Screening of these infections is important to avoid the risk of transmitting infections from blood donors to recipients. Therefore it is a critical part of the transfusion process. The target of this is to make the blood as safe as possible.
Effective screening for those infections can reduce the risk of transfusion. Therefore blood transfusion services should establish an efficient system to achieve this target. All donated blood should correctly screen for specific transfusion transmissible infections. Then only ‘’Non reactive” blood and blood components should released for clinical and manufacturing use.
Characteristics of TTI
The infectious agents or infections usually have some characteristics to be transmitted by blood.
- Presence in the blood for long periods. (Sometimes in high titers).
- Stability in blood stored at 40C or lower.
- Long incubation period before the appearance of clinical signs.
- Asymptomatic or mild symptomatic phase in the affected person (blood donor).
Identification Time of Transfusion Transmissible Infection
The various markers of infection appear at different times after infection. Window period is very much important in this process. Each transfusion transmissible infection has one or more window period, ranging from few days to months. During this period, the particular screening marker is not yet detectable in a recently infected individual.
This can happen even though the individual may be infectious.
Screening Assays for TTI
There are various types of assays for blood screening for these infections.
These assays can detect,
- Nucleic acid of the infectious agents.
These all assays are not suitable in all situations. Each assay has its limitations too.
There are main types of assays used for blood screening tests.
- Enzyme Immunoassays
- Chemiluminescent Immunoassays
- Particle agglutination assays
- Rapid/simple single use assays(Rapid tests)
- Nucleic acid amplification technology(NAT) assays
Screening Recommended Infectious Agents
- Human Immunodeficiency Virus(HIV)
- Hepatitis B Virus(HBV)
- Hepatitis C Virus(HCV)
- Treponema pallidum(Syphilis)
All blood donations should be screened for at least on suitable serological marker for each of these four infections. Screening for additional markers for these infections could then be considered. This should depend on the residual risk and level of resources available.
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