Anti-D alloimmunization after D incompatible platelet transfusions

[cbaldwin]

There is an article on page 650 of the March 2014 Transfusion journal about a 14-year retrospective study at Beth Israel Deaconess Medical Center, Boston Massachusetts that looks at the anti-D alloimmunization rate in D negative patients who received D positive platelets.

 

The article is interesting because it points out the low alloimmunization rate in these patients.  For those of you without easy access to this journal, I will summarize:

 

The article reminds us that most (85%) platelet units transfused in the US are apheresis platelets, and apheresis units contain less than 0.001 mL RBCs, whereas platelet units from WB typically “contain a few tenths of a milliliter of RBCs”.  There is less exposure to the Rh antigen in apheresis platelets.

 

In the study, of 130 D negative patients that received prestorage LR apheresis D positive platelets, none formed anti-D “as shown by negative antibody screens at least 4 weeks after the incipient transfusion.” The patients were 52% male and 48% female.   43% were immunosuppressed and 57% were immunocompetent. 

 

The study started with 626 patients but many had to be eliminated because didn’t conform to the study’s requirements.

 

Of those patients that were eliminated,  354 patients were eliminated  because an antibody screen was not performed greater than 4 weeks after transfusion.  The antibody screen may not have been done because of death, discharge home, etc.  The authors state that this population that was eliminated may have made a difference in the outcome of the study if an antibody screen had been done greater than 4 weeks after transfusion and the population included.

 

However, their conclusion is that the findings “support the use of D+ apheresis PLTs irrespective of Rh status, D+ or D-, in all patient populations without the need for RhIG immunophophylaxis.

 

I think this is interesting and so decided to make a post….

[galvania]

Dear cbaldwin

Thanks for sharing that with us.  I haven't yet seen the paper, but I wonder if it states whether the D+ immunocompetent patients who took part in this study and who did not make anti-D definitely did not receive anti-D prophylaxis at the time?  Because if they did, it rather negates the findings

Thanks

anna

[cbaldwin]

Dear cbaldwin

Thanks for sharing that with us.  I haven't yet seen the paper, but I wonder if it states whether the D+ immunocompetent patients who took part in this study and who did not make anti-D definitely did not receive anti-D prophylaxis at the time?  Because if they did, it rather negates the findings

Thanks

anna

 

Well,

 

There was a total of 626 D negative patients at the start....

 

23 were excluded because they all ready had made anti-D

 

50 were excluded because they received D+ RBCs as well as platelets

 

45 were excluded because they received RhIG

 

16 were excluded because they were allogeneic HSCT patients who had D+ donors

 

354 were excluded because an antibody screen was not performed >4 weeks after transfusion (the range for the ab screen was 4-464 weeks with a mean of 76 weeks)

 

....so that left 130 patients in the study.  I am pretty sure from reading the paper that the immunocompetent patients did not receive prophylatic anti-D.

 

The authors  state:  "We sought to retrospectively determine the rate of anti-D alloimmunization after D-incompatible apheresis PLT transfusions in those patients who did not receive RhIG or D-incompatible RBC transfusions between 1/1/1997 and 12/31/2011.

[galvania]

So actually, the final number is really small.........

[tbostock]

I've only seen it once in my career that a patient made an anti-D from a platelet transfusion.

[AMcCord]

I also have only seen it once - a breast cancer patient.

[marvy1]

I have seen Anti-D alloimmunization a couple times after platelets. Of note, in Canada buffy coat pooled platelets are provided. Some of these products contain a visible amount of blood. I measured one and found >1 mL of packed red cells in a pool. We only suggest Rhogam for Rh Pos women of child bearing age after they get a Rh pos platelet.

[aafrin]

Marvy1_Actually RDPs made by PRP method may have visible red cell contamination, whereas buffy coat platelets usually have almost none or very less red cell contamination. This has been our observation since shifting the method of preparation to buffy coat.

[marvy1]

I'm guessing the amount of blood in either PRP or buffy coat platelets is technique dependent. Both these products, in my experience, have more blood than aperesis, which have an extremely small amount of blood in them.

[L106]

Interesting....Thanks for sharing this info with us, cbaldwin.

 

Donna

[marvy1]

I just received a buffy coat platelet that appeared visibly contaminated with rbcs. Pulled a sample out of it and ran a CBC. The hgb was 1g/L meaning there was approx 20 mL of whole blood in that unit. So as others have asserted that there are next-to-no rbcs in buffy coat platelets, I contend that this statement cannot be universally applied.

[aafrin]

Marvy1, you should talk to your platelet supplier supplier. It seems your platelet concentrates are not adhering to the quality standards for buffy coat platelets.