Strength of anti-D reactions

[JOANBALONE]

Hi everyone,

At our transfusion service we use Ortho gel anti-D. Most pretransfusion specimens react strongly (3-4+) with gel anti-D. Occasionally, we obtain weak reactions with gel anti-D. I am curious how other transfusion services handle weak reactions with gel anti-D when testing pretransfusion samples. Do you test the sample with a different reagent anti-D? Do you have a cut off value in which you would not interpret the Rh as positive? Do you call the patient Rh negative or some other Rh code in the LIS?

Thanks,

JB

[Mary**]

I still have problems calling something that has a clearly positive reaction negative. Confusing to everyone.

[BSIPHERD]

Hi everyone,

At our transfusion service we use Ortho gel anti-D. Most pretransfusion specimens react strongly (3-4+) with gel anti-D. Occasionally, we obtain weak reactions with gel anti-D. I am curious how other transfusion services handle weak reactions with gel anti-D when testing pretransfusion samples. Do you test the sample with a different reagent anti-D? Do you have a cut off value in which you would not interpret the Rh as positive? Do you call the patient Rh negative or some other Rh code in the LIS?

Thanks,

JB

We have developed a third Rh type for these patients - It is *Negative*, so we have Rh Positive, Rh Negative, and Rh *Negative*. The codes we have in our LIS for these is POS for Positive, NEG for Negative, and DEP for *Negative*. DEP comes from Dependent, the Rh type depends... Who actually reports on the patient's chart is: *Negative* *Rh type is dependent on reagents used, tests performed, and/or technical performance. Patient may have been previously reported as Rh Positive or Rh Negative. For Transfusion Service testing, the patient will be treated as Rh Negative and will receive Rh Negative blood for transfusion and/or Rh Immune Globulin. As a Blood Donor, patient will be treated as Rh Positive.*

Our blood tags just print the first 10 characters for Rh so the blood tag for Rh is *Negative*. We have QA set up so that red cells for DEP patient need to be Rh Negative, except for Autologous units.

[noelrbrown]

Bear in mind that the ortho Anti D exhibiting weak reactions may be a partial D type i.e. missing certain epitopes and that the patient may be able to produce an anti D if they are sensitised. Its best to err on the side of caution especially if the patient is Female and of child bearing age. Different monoclonal anti D's have been shown to detect different epitopes of the D antigen so using different anti D's is not a bad idea.