In the recent post we talked about what is plasma donation and where to find & how to donate plasma in pakistan. Read here.
Here we will be clearing some misconceptions about plasma donation
1. Myth: you can only get plasma donation from a same blood group!
Though person’s with the same blood group will be able to donate or receive plasma without an issue. One can also receive plasma from some of other blood groups which will be explained briefly.
There is a difference between blood matching and plasma matching
First lets get some background of whole blood or Red Cell grouping and matching The science behind different blood groups is the antigen present on the Red blood cells in the blood. There are 2 antigens A, B and one other antigen Rh which is denoted by positive or negative on the basis of which almost 8 blood groups are there.
What are antigens?
Antigens are proteins or carbohydrates which our immune system can recognise. Any antigen that is ‘foreign’ to our immune system is destroyed by an antibody.
What are antibodies?
Antibodies are attack molecules our immune system makes to protect ourselves against foreign things such as bacteria and viruses. Antibodies can also be formed in response to different blood groups. Everyone is born
with some antibodies
Red Cells that contain a particular antigen e.g. A contain antibodies against the antigen of B in their blood. This is the reason different blood groups don’t match and will cause red cell breakdown if transfused.
There are some exceptions e.g AB+ is universal acceptor, these persons can receive blood from any group, as their red cells contain all 3 antigens so no antibody against other red cells is present.
Similarly O- is universal donor as this blood is free of any antigen, recipients of any group will accept this blood.
The above is a very simplified one, their are some minor variations which we will not go into the details.
Now lets talk about Plasma, plasma is the component of blood from which Cells (Red, White and platelets) have been removed. This is mostly water and proteins including albumin, globulins, antibodies, electrolytes and nutrients.The point to note here is plasma doesn’t contain any blood group antigen but it has antibodies.
Plasma contains anti-A and anti-B antibodies depending upon the blood group. Our body also has antibodies to A and/or B antigens according to our blood group. Patients should only receive plasma that does not contain an antibody which could attack the antigens present on their own red cells.
Group A recipients have A antigen on their blood cells, so they can’t receive group O or group B plasma as the anti-A will attack their red cells. Group B recipients have B antigen on their red cells, so they can’t receive group O or group A plasma as the anti-B will attack their red cells.
AB blood group recipients can only receive group AB plasma.
Group O recipients do not have any antigen, so can safely receive plasma of any blood type.
Rh antigen is insignificant in plasma donation, hence a patient with (+) blood group can give plasma to (-) blood group of the same type and vice versa.
The image below summarizes the donor and recipient matching for plasma transfusion and matching.
2. Myth: Plasma donation is a cure
The recent media hype about the experimental procedure of plasma transfusion from a recovered case, has led people to frantically search for recovered patients to request for plasma donation, even paying huge sums as per some media reports.
According to the Plasma transfusion guidelines by the Nationa Health services (cite: convalescent plasma guidleines nhsrc.gov.pk) there is limited role in patients with mild to moderate disease and no documented benefit in severe disease.
This is a way of passive immunization and passive immunization works best immediately after exposure, not when the the disease progress has advanced.
3. Myth: Every Recovered patient can donate plasma
For the plasma to be beneficial as a therapy the recovered persons should have antibody levels above the minimal threshold otherewise it will not be beneficial, ideally every plasma donor should have his/her antibody titres done.
Hope this discussion clarifies some misconceptions, have anything to say comment below.