Transfusion Medicine I Flashcards
What are the molecular propertiesof ABO antigens present on RBCs?What are some of the other antigens present on RBCs?
Oligosacchardies (not proteins)Some other antigens are amino acid sequences called Rh, Kell, Duffy etc which are less clinically significant.
What is the most common hemolytic syndrome observed clinically involving ABO antigens?
Mother with O blood group developing IgG antibodies against fetus that has A blood group, only IgG antibodies can cross the placenta, leading to hemolytic syndrome, we see increased bilirubin in this case.
What kind of antibodies are present in the plasma of different patients?
Mostly IgMs except patients with O phenotype also develop IgG in addition to IgMs.
What are the different types of Rh antigens?What kind of antigen is Rh?When are these antigens clinically tested for?
- Rh is a protein antigen present on RBCs. 3 genes on Ch1: RhCEand RhD
- Encode 3 Ags: D Ag, C/c Ag and E/e Ag
- CE are always together so CE Ag has 4 combination: CE, Ce, cE, ce
- D gene has 2 expression condition: D (expressed) and d (not expressed) (there is NO “d” gene)
- Patients are not routinely typed for CE antigens unless there is a history of developing antibodies against these proteins
- By far majority, most of the people are Rh positive (have D antigen, d = Rh negative)
What are weak D and partial D antigens?
Can you develop antigen RhD Ab during platelet transfusions?
Chance is about 1%, this is because we cannot seperate all the RBCs from platelets, important to know that Rh antigen is NOT expressed in platelets.
What are some other examples of protein antigens on RBCs?
These are rare and do not have significant clinical concquences, just know that these exist.
What is the immediate spin test?
Important to know that it only checks for IgMs.
What is the single most important test for RBC Ab detection?
Antiglobulin test (AGT, Coombs’ test)
- Most important single test in RBC Ab detection
- AHG helps to bridge adjacent sensitized RBC (with IgG or complement) and results in agglutination Types
- Direct Antiglobulin Test (DAT) - detects patients RBCs that have been coated with IgG or complement
- Indirect Antiglobulin Test (IAT) - detects anti RBC Ab in patients serum
What is the procedure for ABC typing?
There are 2 tests done, forwards type and reverse type. In each test we are checking for the RBC antigens and the present of anti RBC Ab in patient’s serum
What is the protocol for transfusion of different blood products?
Define the major cross match and minor cross match; know the clinical significance of major crossmatch.
Major crossmatch: assess the compatibility of a donor RBCs with the recipient plasmaMinor crossmatch: test the donor’s serum/plasma with recipients RBCs, rarely done clinically.XM = cross match.
