I have a question. We have a patient in our hospital who has an anti-CSa. This antibody was identified by the red cross, when we sent the patients specimen out to them. I am just curious to know, how exactly is an anti-CSa identified? I mean, are there actually panels out there that you can rule out HLA antibodies on? Is there antisera for such antigens? Please share any info if you know!

I have a question. We have a patient in our hospital who has an anti-CSa. This antibody was identified by the red cross, when we sent the patients specimen out to them. I am just curious to know, how exactly is an anti-CSa identified? I mean, are there actually panels out there that you can rule out HLA antibodies on? Is there antisera for such antigens? Please share any info if you know!

Cs(a) and its associated antibody were first described by Giles et al, and I am intensely proud to say that I worked at the Blood Group Reference Laboratory in London in Carolyn Giles' Laboratory in the 1970's, when Joyce Poole was the Senior Medical Laboratory Technician (as Biomedical Scientists in the UK were called at that time).

Cs(a) is not an HLA antigen (i.e. an antigen adsorbed onto the red cell surface, like Bg(a)), but a "genuine" red cell antigen, and the antibody is amongst the group previously termed HTLA (HighTitre, Low Avidity), and still called that by some (including me), until another proper description is defined!

Cs(a-) red cells are comparatively rare (about 98% of Black and White individuals are Cs(a+)), but even rarer are red cells that are actually typed for the Cs(a) antigen. This is mostly because a "typing" anti-Csa (i.e. one that is strong enough to rely on for grouping) is "as rare as hens' teeth".

That having been said, many Reference Laboratories do have such cells available to them, and, yes, it is possible to type the antibody using these cells. The problem is, like many other such antigens, the expression of the Cs(a) antigen on red cells is very weak, and vries greatly from individual to individual, and so typing should only be performed by reliable Laboratories.

The good news is that anti-Csa is clinically benign.

:):)