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TRANSFUSION-TRANSMITTED DISEASES Blood is a lifesaving resource and blood components should be tested so that it makes them extremely safe and reduces the risk to minimum of the likelihood of a transfusion-transmitted disease (TTD). TTD is the infectious complications of blood transfusion. A variety of infectious agents including bacteria, viruses, parasites (Table 15.5), and prion pathogens can get effectively transmitted through blood transfusions. If they are not detected in the testing process, it can cause harm and even death. Screening Blood Donors for Transfusion-Transmitted Infections Donor Testing Once a donor passes the medical screen and donor questionnaire, the serologic tests should be performed for the TTD. Routine screening of donor’s blood in India is presented in Table 15.6. Performing these tests can make blood transfusion safer than ever before. Apart from the transfusion-transmitted diseases listed in Table 15.5, many other organisms may also be transmitted by transfusion. However, tests for these organisms are not routinely performed in the blood screening process. These include other viruses, such as Epstein-Barr virus (EBV), cytomegalovirus (CMV), parvovirus B19, bacteria (presently is the leading cause of death from transfusion), parasites, such as Babesia microti and Trypanosoma cruzi, malaria, and prion diseases. Presently performed test methods are extremely sensitive. Hence, confirmatory tests are used only to detect false-positives. These tests depend on the disease to be confirmed and include polymerase chain reaction (PCR), Western blot (WB), radioimmunoprecipitation assay (RIPA), and recombinant immunoblot assay (RIBA).It is important to select a safe donor to provide a safer donation. The safest donors are regular, voluntary, and nonremunerated. Blood for donation should be screened for TTDs. Test samples: Most of the assays use either serum or plasma. The instructions with the assay must be followed strictly.Mandatory Screening Tests The five tests that are mandatory as per Food and Drug Administration (FDA) for the donated blood units are HBsAg, HIV Ab, HCV Ab, VDRL and malarial parasites. Nucleic Acid Testing (NAT) or Nucleic Acid Amplification Test (NAAT) NAT is a general term used for molecular-based methods of screening for infectious agents. A nucleic acid test (NAT) is a method useful to detect a particular genetic material (nucleic acid) of virus or bacteria which acts as a pathogen in blood, tissue, urine, etc. The NAT differs from these conventional tests in that it detects genetic materials rather than antigens or antibodies. It detects very low numbers/levels of RNA or DNA of the pathogens (e.g., HIV, HBV, HCV) in the bloodstream before the appearance of antibodies. It detects infection earlier than conventional methods thereby narrowing the window period. In concise form to study for exams
ASSISTANT
**Transfusion-Transmitted Diseases (TTDs)**
- **Definition**: TTDs are infectious complications that arise from blood transfusions involving various infectious agents such as bacteria, viruses, parasites, and prions.
**Common Infectious Agents**:
- **Viruses**:
- Human Immunodeficiency Virus (**HIV**)
- Hepatitis B Virus (**HBV**)
- Hepatitis C Virus (**HCV**)
- Epstein-Barr Virus (**EBV**)
- Cytomegalovirus (**CMV**)
- Parvovirus B19
- **Bacteria**:
- Leading cause of death from transfusion-related infections.
- **Parasites**:
- **Malaria** (Plasmodium species)
- **Babesia microti**
- **Trypanosoma cruzi**
- **Prions**:
- Agents causing diseases like Creutzfeldt-Jakob disease.
**Donor Screening and Testing**
- **Importance**: To ensure the safety of blood transfusions by minimizing the risk of transmitting infectious diseases.
- **Safe Donor Criteria**:
- Regular donors who are voluntary and non-remunerated.
- Pass medical screening and donor questionnaire.
- **Test Samples**:
- Mainly serum or plasma.
- Strict adherence to assay instructions is crucial.
**Mandatory Screening Tests** (as per FDA guidelines in India):
1. **HBsAg**: Hepatitis B surface antigen
2. **HIV Antibodies**: Detection of HIV infection
3. **HCV Antibodies**: Detection of Hepatitis C infection
4. **VDRL Test**: Screening for syphilis
5. **Malaria Parasite Test**
**Advanced Testing Methods**
- **Nucleic Acid Testing (NAT)/Nucleic Acid Amplification Test (NAAT)**:
- **Purpose**: Detects genetic material (RNA/DNA) of pathogens, identifying infections earlier than antibody or antigen tests.
- **Benefits**:
- Narrows the "window period" where infections are undetectable.
- Increases the safety of blood transfusions by early detection.
**Confirmatory Tests**
- Used to confirm positive results and rule out false positives.
- **Methods Include**:
- **Polymerase Chain Reaction (PCR)**
- **Western Blot (WB)**
- **Radioimmunoprecipitation Assay (RIPA)**
- **Recombinant Immunoblot Assay (RIBA)**
**Key Points for Exam Preparation**
- **Understanding TTDs**: Know the types of pathogens that can be transmitted via blood transfusion.
- **Donor Selection**: Recognize the importance of selecting safe donors to enhance transfusion safety.
- **Mandatory Tests**: Familiarize yourself with mandatory screening tests and their role in preventing TTDs.
- **Advanced Testing**: Understand how NAT/NAAT improves early detection of infectious agents.
- **Confirmatory Testing**: Be aware of confirmatory tests used to validate initial screening results.
By focusing on these key areas, you can prepare effectively for exams on transfusion-transmitted diseases and blood safety protocols.