Hi we had patient who has known anti E antibody. He has been transfused with 2 units E- K- by IAT xmatch.  2 weeks iater we received sample for G/S and request for 1 unit of blood due to low Hb. However clinician haven't suspected  any transfusions  reaction. Performed antibody screen and found to be positive with Anti-E and Jka with DAT positive in IgG 1+ and C3d 2+. 

Would this be a transfusion reaction? Or patient had developed new antibody due to recent transfusions?  What is reason for DAT to be positive in C3d as well?

I think IgG antibody causes extracascular haemolysis . Is it due to antibody develop recently that might be IgM in nature ?

Thanks in advance 

Kidd system antibodies can bind complement.

To investigate the reason, maybe you should do an elution, then test the eluate to see what specity /specities of the binding antibodies.

Add fresh serum can strengthen the sensitivity of testing Kidd antibodies.

Edited October 22, 20195 yr by yan xia

The first thing to say is that the laboratory personnel cannot diagnose a transfusion reaction.  This may be a delayed haemolytic transfusion reaction, where the patient is clinically compromised, or it may be a delayed serological transfusion reaction, where the sample from the patient tests for a positive DAT and a "new" antibody specificity, that can be eluted from the red cells, but where the patient is not clinically compromised.  This can only be diagnosed by the physician looking after the patient.

Secondly, the anti-Jka may be a de novo specificity, or may be present in the circulation as a result of an anamnestic reaction.  Certainly, two weeks seems a bit quick for a de novo specificity to be detected, but it can happen (never say never in blood transfusion!), so it is more likely to be present as a result of an anamnestic reaction, although there must be a certain proportion of IgM immunoglobulin, as well as IgG.

As yan xia says, Kidd antibodies can cause complement fixation, but can only so do if there is some element of IgM present (anti-Jka that is pure IgG cannot fix complement), however, it is incredibly rare for Rh antibodies to fix complement (as far as I know, there are only two examples of anti-D described in the literature that have been able to fix complement - and just think how many millions of anti-D have been detected), so the complement on your patient's red cells is much more likely to be there as a result of the anti-Jka, than the anti-E.

Adding fresh serum does increase the sensitivity of the test (the so-called "two-stage IAT"), but treating the red cells with a protolytic enzyme, such as papain, and then performing the IAT is even more sensitive.  An eluate can be used to "concentrate" the antibody sensitising the patient's red cells, but, be careful, as, is you are using a commercial elution kit, this may go counter to the kit instructions.

Applied Blood Group Serology, 4th Ed. chapter 6, pages 129-132 addresses complement activation by blood group antibodies.  It's an interesting read.  This is the verbiage we use with a recently transfused patient that has demonstrated a positive DAT, a new antibody in the eluate and perhaps in the plasma/serum: "Serologic results, including a positive DAT due to IgG and complement (C3d), support the occurrence of a delayed serologic transfusion reaction."  The DAT portion may be edited as needed.  We're not making a diagnosis, but simply altering the physician to its possibility.  

Thanks everyone 

Clinician hasn't suspected transfusions reaction and hasn't asked for any investigations. This is something we noticed the results when they requested further blood unit.   just wanted to know causes of DAT to be positive in C3d therefore shared on discussions board.