Pre-transfusion Blood Tests: Title: To perform the following tests: ABO and RH grouping using the Diamed Gel Card system. Rh and Kell phenotyping (antigen typing) using the Diamed Gel Card system. Direct Coombs Test (DCT) using the conventional tube system. Direct Coombs Test (DCT) using the Diamed Gel Card system. Antibody Identifications (IAT) technique using the conventional tube system. Antibody Identifications (ETC) technique using the Diamed Gel Card system. Name: S. Ward Date: 8/11/2012 Introduction: The objective of this practical is to perform some pretransfusion tests, using various methods.
Pretransfusion testing is carried out in all hospital blood bank laboratories and is used to minimise the risk of encurring a haemolytic transfusion reaction. Haemolytic transfusion reactions occur when a patient is transfused with red cells which have a foriegn antigen on the cell surface that the patient has an antibody to. While the ABO and Rh blood group systems are the most antigenic and thus can cause severe haemolytic transfusion reactions. The other blood group systems can also cause a (less severe) haemolytic reaction, these reactions can be fatal and so the procedures to avoid them are of great importance.
Materials & Method: Not all tests were performed by all members of the class. ABO and Rh blood grouping using the Diamed Gel Card system; performed. Rh and Kell trying using the Diamed Gel Card system; not performed. Direct Coombs Test (DCT) using the Diamed Gel Card system; not performed. Antibody Identification (ETC) technique using the Diamed Gel Card system; performed but not centrifuged so no results were obtained. Antibody Identifications (IAT) technique using the conventional tube system; performed Direct Coombs Test (DCT) using the conventional tube system; erformed. Cell 1% suspensions were prepared for the bench from a 3% cell suspension provided. Results: As well as some tests not being completed by everyone, some results were not obtained as there was a queue for the ID centrifuge. Results below are ones obtained by myself; ABO & Rh grouping; Known O+ cells were tested. Expected results would be; However, the gel matrix had dried out so no results were obtained. Antibody Identifications (IAT) technique using the conventional tube system; + + + – – + – – + +
When these results are compared with the ID panned profile, its is seen that there is no antigen which matches the antibody in the patient’s plasma. Traditional Direct Coombs test results was positive. Discussion: The results from this practical were not as expected. With regard to the ABO Rh typing, the expected result for the O+ blood tested is as shown above. The reason why the results obtained were incorrect were because the gel had dried out. This shows that it is very important to ensure that the reagents used in the transfusion laboratory are of a really high quality to ensure that all results obtained are reliable.
With regard to the traditional antibody profile, it is seen that there is no antigen which matches the antibody in the patient’s plasma according to the ID panel. It is possible that the patient has an uncommon antigen which isn’t on the ID panel. However, it’s more likely that there was human error in labelling the reaction tubes 1-10. The direct coombs test checks to see in vivo sensitisation to IgG antibodies. The traditional coombs test results for this practical showed aggultenation when treated with antihuman globulin, which is a positive result.
Results for the other laboratory tests using Diamed Gel Card system were unobtained due to there being a queue for the centrifuge. A brief explanation of all these tests is explained below; ABO & Rh D grouping; this can be done by conventional tube technique, as performed previously, or can be done using the Diamed Gel Card system. These gel cards contain known antobodies on a gel matrix. A positive result shows the red cells kept at the top of the gel matrix, a negative result sees the red cells going down through the matrix to the bottom of the card.
This has replaced the traditional method as it allows for automation. Rh & Kell phenotyping; this is done using the Diamed Gel Card sytem and is similiar to the ABO and Rh typing method. This shows which, if any of the main Rh or Kell antigens are on the patients red cells. The results are read in the same manner as the ABO and Rh D as described above. Direct Coombs Test using the conventional tube system; The direct antiglobulin test is used to detect in-vivo sensitisation and detects small IgG antibodies on a patient’s red cells.
The conventional tube method involves washing the cells three times for one minute, resuspending each time, then finally adding two drops of antihuman globulin and centrifuge once more for 20 seconds and results were recorded. This process is laborious and so can be replaced with the next method. Direct Coombs Test using the Diamed Gel Card system; The gel card system involves the addition of 1% cell suspension of test cells to the Anti IgG card, this is centrifuged for 10 minutes and results are recorded. This method also shows in-vivo sensitisation and detects small IgG antibodies on the patient’s red cells.
Antibody Identifications (IAT) technique using the conventional tube system; Antibody identification is used as a follow-up test to a positive indirect antiglobulin test. The antibody identifcation test is used to determine the red cell antibodies in the patient’s plasma. If one or more clinically significant red cell antibodies are identified, then donor blood that lacks the corresponding red cell antigens must be used for tranfusion, this is reffered to as antigen negative blood. The conventional tube system involves reacting the patients plasma with the 10 commercial identification cells.
This is incubated for 30 minutes at 37°c, each of the reaction tubes are washed 3 times for one minute, resuspended after each time and then two drops of antihuman globulin are added and the tubes are centrifuged for an additional 20 seconds and results are recorded. This process is laborious, and so can be replaced by the gel card system which can be automated. Antibody Identifications technique using the Diamed Gel Card system; The method is the similiar to the other gel card systems and the principle it the same as the other antibody identification.
As mentioned bofore, this process allows for automation and so is favoured in large labs. Questions: Principle of the Direct and Indirect Coombs test: The principle of the Coombs’ test is that addition of rabbit anti-human IgG to the patient’s blood will result in aggregation of the patient’s red cells if the red cells are coated in small IgG antibodies that will not agglutenate normally at room temperature. So, the direct antiglobulin test is used to detect in-vivo sensitisation to IgG antibodies. Applications:
The direct coombs test is udes to test for autoimmune haemolytic anaemia. The indirect coombs test can be used to detect very small amounts of antibodies present in a patients plasma and if used in antenatal care to screen pregnant women for antibodies that may cause haemolytic disease of the newborn. It can also be used for compatability testing, antibody identification, RBC phenotyping and titration studies. Controls: The positive control is sensitised O+ cells and the negative control is O- cells.