BLOOD GROUPINGS

 

1. Introduction

There are several blood grouping systems known to exist in humans. The most crucial system for screening, transfusion, and transplantation practices today is the ABO blood grouping system. Based on the presence or absence of antigens A and B on the surface of RBCs and naturally occurring antibodies anti-A and anti-B in serum, the ABO blood grouping system classifies blood into four groups (A, B, AB, and O). Antigens and antibodies have a mutually beneficial interaction in healthy human blood as seen below:

  Forward grouping is a known anti-A and anti-B sera, red blood cells are examined for the presence of A and B antigens. Red blood cell agglutination with a certain reagent is a positive test result that shows the red blood cells have the appropriate antigen present.

 Reverse grouping is a serum grouping with known A and B red cells are used to test serum for anti-A and anti-B antibodies. The relevant ABO antibody is present when A1 or B reagent red cells are directly agglutinated with the patient's blood or plasma.

On specimens from all patients older than four months, forward and reverse typing will be done in order to confirm typing and uncover subtypes. Babies younger than four months old could not have generated enough antibodies to enable detection. Before specimen collection, the patient does not need to be specially prepared. The sample should be tested as soon as feasible after collection, but if testing is delayed, EDTA and clotted specimens can be kept at 2 to 8 C for up to 10 days. (Note: Storage may cause reactions to be weaker than usual.) The specimen's bacterial contamination could result in inaccurate test findings.

1.2 Tube method procedure for forward grouping.

Prepare a suspension of 3-5% red blood cells in isotonic saline for testing. After preparation, put one drop of each antigen Anti-A and Anti-B into two tiny, appropriately labeled test tubes. Additionally, mix in one drop of RBC suspension in the tube. The test tube should be centrifuged for the recommended amount of time. Resuspend the cells after centrifugation are complete, and then look for agglutination macroscopically. Hemolysis shouldn't be viewed as a good sign because it can be a sign of bacterial infection. After completing the test method, record the results and note the grade.

1.3 Tube method procedure for reverse grouping.

To verify the reverse grouping method label a test tube for each RBC reagent that will be tested. Each labeled tube should have two (2) drops of serum or plasma and one (1) drop of A1 cells or B cells, respectively. Centrifuge the test tubes for the necessary amount of time after mixing to resuspension the cells. Examine the cells under a microscope for agglutination after they have been resuspended, and record the outcome.

1.4 Interpretation of test results: + (agglutination) 0 (no agglutination)

Unknown cells with: Unknown serum with Interpretation Caucasian Freq. (%)

Anti-A Anti-B A1 cells B cells Group

+ 0 0 + A 40

0 + + 0 B 11

0 0 + + O 45

+ + 0 0 AB 4