Q. I have a question about blood typing. I understand that in forward typing, we use anti-A and anti-B antibodies. I was wondering how you know which antibody caused the agglutination, and how do you find out what type of blood is in there. Do you do two forward typing reactions, first with Anti-A then with Anti-B?
A. You’re exactly right – you do two reactions: one with anti-A and one with anti-B!
When you do forward typing, you use antibodies that you buy from a company. So you have a little tube of anti-A antibodies and a little tube of anti-B antibodies. You take one test tube, drop a few drops of the anti-A antibody reagent in there, and add a drop or two of the patient’s blood. If you see clumping, you know the patient’s blood must have A antigen on the red cell surface. You repeat the same procedure in a new test tube, this time with the anti-B antibody reagent.
Usually you do the forward typing first, just by convention, but you wouldn’t have to. Both the forward and reverse typing need to be done and they need to match up (if the patient has type A blood on forward typing, he/she should have anti-B antibodies on reverse typing). The order in which you perform the tests doesn’t really matter.
please let me know the importace of revese blood grouing ? why we have to report blood group after both mehod forward & reverse blood grouping method ?
That’s a great question! Rarely, a patient will have a blood group antigen that is not detected by forward typing. For example, they may be of AB type, but the B antigen is really weak or is not picked up by forward testing for other reasons. So it’s important to do the reverse typing as a cross check. If the results don’t agree (i.e., if you get type A on forward typing, but the patient has no anti-B antibodies on reverse typing), then you need to do more exploring to figure out why. Sometimes, it’s just a clerical error – so the first thing you usually do is simply repeat the test with the same specimens.
Having both forward and reverse typing is also good for exactly that reason – to pick up clerical/technical errors. We are human beings – so there is the potential for making a mistake. With a built-in cross check, you run much less risk of mis-typing the patient.
What is Bombay blood group
It is a very rare blood group in which patients do not have the H gene (which encodes an enzyme that helps form the H antigen, which is the structure that forms the basis for the A and B antigens). Almost everyone in the world has the H gene – so almost everyone has the H antigen. People who have the A gene add N-acetylgalactosamine to the H antigen to make A antigen. People who have the B gene add galactose to the H antigen to make B antigen. So patients with Bombay phenotype have a very difficult time getting transfusions – if they get a transfusion from anyone except another person with Bombay blood type, they will react to the H antigens present in the donor blood.
Do people with O blood group also have H antigen?
Yeap. The O blood group actually has the highest concentration of H antigen
Why is blood group O+ not a universal donor
Thanks for your question! It was so good I decided to make a post out of it.