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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.

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.

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.

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.

I'm with David on this one. Doing both paper and computer entry just adds one more opportunity for mistakes. If you can't trust some one to put it in the computer correctly how can you trust them to write it down correctly! The key is the ability to enter the results as they see them and not have to walk over to a computer station to do it. Also, if you are entering from an instrument print out I highly suggest you get that instrument interfaced as quickly as possible. Again, you are entering results from paper and that should be avoided.

Stop using paper once you have your BBIS validated. It is just as easy to type 4 as to write 4+. The system shouldn't let you make interpretation errors. Trust it. I know I've been turned down for positions because I told the technical staff that their papers would be history from my day 1. I also have inspected places that did the paper first. Went to watch a transfusion and had to return because the patient needed irradiated products - only found in the computer. It was a good lesson that you don't want repeated when you get inspected.

Ortho gel is known for picking up weaker D antigens than some tube reagents. I know that Quotient/Alba anti-D blend reacts more like the Ortho gel but the Immucor Gammaclone doesn't pick up those (mostly) weak D types 1 & 2 at IS. They will show up positive at AHG phase with Immucor. John Judd published a paper, which many follow, of considering anything 2+ or weaker in gel as Rh negative. I assume if you take the tube testing through AHG you will get a positive. Doing that will help troubleshoot the situation. None of this probably has much to do with the transfusion reactions. Rh typing of weak and atypical D antigens is a complicated mess both serologically and the terminology. If these are young females, we try to send them for molecular D typing.