preview:• Cross matching forms a key component of blood transfusion – it is ultimately what we do – we are gong to make sure the blood we give to a patient form the donor is compatible.
• Many reasons when a blood transfusion is required form being involved in a road traffic accident or su...
Despite all the efforts we put in over many years, transfusion reactions still do occur so it’s
important to be aware of what they are, how they arise and how we deal with them within
the blood transfusion laboratory.
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There are 39 human blood group systems of which 9 are important within humans.
One is rhesus and within that is rhesus D – you see this in HDNB.
Depending on what antigens your red cells express will depend what blood group you are.
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1901 – considered to be the father of blood transfusion.
Bed some of his employees and reacted the serum of some with others and noticed that
there were some agglutination reactions which gave rise to modern blood transfusion
29 years later in 1930 he was given a Nobel prize for this
If you have blood group A you will lack an anti-A antibody etc.
The ABO blood group system remains the only system that we can say with confidence – all
of the others we have to screen.
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Strict acceptance criteria because we want to minimise the potential risk to the patient, we
don’t want them having a transfusion reaction or any sort of negative consequences which
can range from a lifechanging even they have to live with all the way to killing them.
Pre-printed labels won’t be accepted have to handwritten next to the patient’s bedside and
signed with the person collecting the blood or it must be a blood turn label.
This is what the samples and form look like – pink tops allow it to be distinguished from
routine haematology.
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Cross matching forms a key component of blood transfusion – it is ultimately what we do –
we are gong to make sure the blood we give to a patient form the donor is compatible.
Many reasons when a blood transfusion is required form being involved in a road traffic
accident or surgery (elective surgery where they might need blood) or for a patient that
undergoes a major haemorrhage during surgery which was unpredictable and therefore will
require lots of blood. Other reasons are listed on the slide.
In the group part of this term the grouping is to determine the patients ABO and rhesus
status of the patient (whether or not the express rhesus D).
The screen part is to determine whether the patient has any detectable levels of antibodies
that are of interest to us clinically as they may cause a transfusion reaction, so we need to
detect them.
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When performing a crossmatch, we need to take a lot of other information (second bullet
point) – in terms of location that would mean where they are currently based so are they in
theatre of A&E.
CMV – cytomegalovirus.
In the case of new-born babies, if the mum is CMV negative and the baby is CMV negative
we want to give CMV negative blood because CMV is very problematic in children, so we
want to make sure that the cause of developing CMV is not from the blood that we have
given them.
, 11. Transfusion Reactions
Any blood tubes or forms that we receive it is important that they are signed by a particular
member of staff who is taking the sample so we know what that member of staff is, and we
can contact them – this is important as problems in communication are a huge source of
blood transfusion errors, they can give rise to transfusion reactions.
In order to perform a crossmatch, we require two samples, the first is what we refer to as a
historic sample – it is the first tube we receive in the blood transfusion laboratory of which
we will determine the patients blood group and if they have any antibodies that are of
particular significance. Then we will require a second sample and we will re-perform that
blood group and antibody screen to confirm the results of the first sample that we received.
We want to make sure we get the exact same blood group, and we are not seeing any new
antibodies formed.
If however the patient requires a blood transfusion and the second (most recent) sample is
no longer valid, we will then require a third sample because we don’t know in that time form
the last sample we received if it’s been a long time whether the patient has developed any
new antibodies which we need to take into consideration.
It is important that the two samples (the historic and more in date one) have been obtained
on two separate dates, times are members of staff with two separate request forms and
ideally from two separate venepuncture sites.
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The most rapid – can perform in 5 minutes.
It doesn’t require any wet lab work (BMSs physically doing the cross match within the
laboratory).
LIMS – basically the laboratory database.
Non-serological issue because we are not physically testing the patients’ blood against the
donor blood, it is all going to be performed electronically.
As it is electronic there is a very strong criteria for the patient to be eligible for the cross
match to be performed.
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We have the patients’ blood group results and also their antibody screen results – we will go
into the stocks of donor blood we pull out the packs that we believe will be compatible
based upon these results.
2 – we will label the card with the patient details and which packs we are going to put within
each well.
In essence we are adding donor red cells and patient’s plasma which should contain any
antibodies.
Much like the direct antiglobulin test this card here contains anti-human globulin so if the
patient as antibodies that bind to the donors red cells, they will form an antigen antibody
complex and the anti-human globulin will from that matrix that we see in the direct
antiglobulin test – when we spin the gel card down these antigen antibody complexes will
become trapped within the column.
1, 3, 4, 5 are negative – those red cells have been able to drop following centrifugation
therefore no antibodies are binding to them, so no complex is formed – in donor 2 we are
getting antibodies and a reaction between the patient’s antibodies and the donors red cells
so they are forming an antigen-antibody complex, so they are not compatible.
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Once we’ve performed that cross matching and identified which units of blood, we are going
to issue to the patient requiring the blood transfusion it is important that we ensure the
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