Malcolm Needs - Special Moment for A Blood Group Serologist

There was a very special moment in my career, of which I am very proud. It happened one night when I was due to be “on-call”. At the time in the reference lab, I worked a day shift (06:30-15:30) with on-call to begin at 17:00 hrs.

We received a sample into the Reference Laboratory during the afternoon, taken from a gentleman who was due for surgery the following day. It became clear that he had a strong anti-K in his plasma, but also another weaker antibody directed against a high prevalence antigen of unknown specificity.

Like all good and true people who work “on-call”, I was desperately hoping that the specificity could be identified before 17:00 hours (when the on-call duty started), but it was not to be! Once the sample arrived, and was shown to be difficult, I stayed in the laboratory until it was resolved. 
 
All I knew at this stage was that the antibody was not an auto-, but an allo-antibody, that it was detected equally well by IAT and with papain-treated red cells, that the antibody was not inhibited by AB plasma, that the specificity was not one of the more “common” rare specificities (in terms of relativity of its rarity), such as an anti-U, an anti-Lu3, an anti-Kp^b, an anti-Fy3, an anti-Jk3, an anti-I, an anti-Lan or an anti-Vel, and that it was down to me to sort it out!

I tested the plasma against a whole raft of liquid K- red cells with “rare negative antigens” that we had in the laboratory, but got nothing compatible. I did not particularly want to thaw any other rare red cells at this point, as (a) it is a bit of a long-winded affair to so do, and (b) it could be a terrible waste of a lot of rare red cells, as I still had no idea as to the specificity.

Instead, I decided to thaw a collection of rare antisera and tackle the problem from the “other side” as it were (fortunately, the patient was group O). I was lucky in that we had a fine collection of rare antisera, some from SCARF and others from our own patients’ samples. At this stage, it was a “screening” exercise and so I did not use controls (don’t tell Quality!).

• Four different specificities gave negative reactions, and so these were retested with a positive control. 
• Three of the specificities gave negative results with the positive control, showing that the antibodies in the samples were no longer viable.
• One still gave a negative reaction with the patient’s red cells, but a positive reaction with the positive control. 
• Had I cracked it? No, not yet. 
• We were lucky enough to have three other examples of the antibody specificity frozen. The patient’s sample was compatible with all three! 

The specificity with which the patient’s red cells were compatible was an anti-Er^a. So, had I cracked it? No, not yet. I had shown that the patient was Er(a-), but that did not mean that the specificity of the antibody in the patient’s plasma was anti-Er^a; it could be that the patient was negative for another, unidentified, high prevalence antigen, and that the antibody in his plasma was directed against this second high prevalence antigen.

I thawed out the three examples of K-, Er(a-) red cells that we had and tested these against the patient’s plasma. All three were compatible and so, therefore, the patient had an anti-K+Er^a in his plasma, and it still just before 22:00 hours!

Identifying the anti-Er^a proved to be a bit of a pain, to say the least, and we had no Er(a-) units of blood frozen, but, the good news is that anti-Er^a has never been known to be clinically significant, and so the surgical procedure went ahead (and the patient did not require blood).

What made this so much fun (apart from solving a difficult case) was that, when we sent it down to the IBGRL for confirmation, Joyce Poole told me that (a) I had got it correct and (b) that it was the first example of an anti-Er^a found in England (although not in the UK, as one had previously been detected in Wales).

As with the discovery of the novel Partial D types, and the novel background to the D - - phenotype, it is the excitement of finding something “new” that adds that extra bit of fun to work!