Chapter 14 Testing of Donor Blood Flashcards
What two categories can donor tests be divided into?
- Immunohematologic testing (Type & Screen).
- Infectious disease screening.
What immunohematologic ABO, D and K tests are done on donors?
ABO, D and K testing
1. Forward and reverse testing is performed
2. Weak D testing is performed on all negative donors
3. K antigen testing is now performed on donors - if it comes back negative twice, it is indicated K negative on units.
What other type besides ABO, D and K phenotyping is done on a subset of donors?
Phenotyping for C,c,E,e,Jka, Jkb, Fya, Fyb, S,s is routinely performed on a subset of donor samples. This helps find units quickly for those that have clinically significant antibodies.
What type of genotyping is done on some donor units?
Red blood cell antigen genotyping is also done on some donor units. This allows for identification of certain rare phenotypes
What are different ways the antibody screen can be done? How do the results affect the usage?
Antibody screen
1. Screening cells can be separated or pooled
2. If significant antibodies are present, plasma and platelets cannot be used
RBCs can be used, but the antibody interpretation should be on the label
Describe in general the testing program for transmissible disease in donor blood by CBS?
- There are lab tests performed on every donation to detect specific agents:
- These are for diseases that are easy to test for and known to be transmitted through blood
- This helps to keep the Canadian Blood System safe
- These are not run at all CBS locations but sent to large centers in Alberta and Ontario.
Are all diseases tested for in the donor’s blood?
Some diseases cannot be easily tested and are only ruled out by the screening questionnaire
What is HIV-1/2?
Human Immune Deficiency Virus (HIV) - 1/2 cause Acquired Immunodeficiency Syndrome (AIDS)
Infects CD4+ T lymphocytes (helper T cells)
What is the testing required for HIV-1/2?
Screening tests
1. Antibody to HIV - 1/2 develops 22 to 25 days after infection (chemiluminscent assay)
2. HIV NAT – run on pooled donor plasma (6 patients put together)
Confirmatory/Supplemental Tests
1. Anti-HIV-2- EIA
What is HBsAg?
Hepatitis B surface antigen (HBsAg)
HBsAg is a protein on the viral surface; it indicates that the individual is infectious
When does the antibody to HBsAg appear?
Antibody to Hepatitis B core antibody (anti-HBc)
–>Antibody appears after HBsAG but before symptoms
When is Anti-HCV detectable?
Antibody to HCV
–>Anti-HCV antibody is detectable 10 weeks after infection
NAT (Nucleic Acid Testing) to detect DNA of HBV and RNA of HCV (pooled samples)
See slide 10 for table of testing for various Hepatitis viruses.
What is the requirement for testing for Human T-cell Lymphotropic Virus-I/II?
- It is a requirement that all donor blood be tested for antibody to HTLV types I and II
- Screen is done by chemiluminescent assay. Confirmation by HTLV Western blot
Note:
HTLV-I is associated with adult T-cell leukemia
HTLV-II is associated with large granular lymphocyte leukemia
What is the name of the bacterium that causes syphilis?
Syphilis is caused by Treponema pallidum
Spirochete bacterium
What tests (3) are there that can detect a the presence of the bug that causes a syphilis infection? Which one is the screening test?
- Rapid Plasma Reagin Test
Non-specific for T. pallidum, detects reagin which is released during Syphilis infection - Treponemal Tests
a) Microhemagglutination - Sensitized sheep erythrocytes coated with T. pallidum react with patient IgM or IgG antibodies
b) Fluorescent treponemal antibody adsorption