Antigen typing patients with anti-D

[BloodbankZ 1]

What are other people's institutions practices on the following. If you have a patient with an anti-D do you need to go ahead and carry out the D antigen typing on the patients rbcs through the IAT phase(weak D testing)? The AABB 18TH ed. Technical Manual states on pg. 327 "When the D type of a patient is determined, a weak D test is not necessary except to assess the red cells of an infant whose mother is at risk of D immunization."  It then goes on to say under Identification of Antibodies to Red Cell Antigens pg.401 "Determining the phenotype of the autologous red cells is an important part of antibody identification."  We use MTS gel for as our primary method for blood type determination and it states that Most weak D antigen expressions will be detected(which means not all), however partial DVI epitope variant of the D antigen will not be detected with this monoclonal reagent. Not that it really changes how we transfuse the patient but just curious to others procedures/thoughts. Thanks in advance.

[Malcolm Needs ★ 4,543]

The only thing I would do, once the patient has been found to be (initially) D Negative, is to perform a DAT, to show whether the anti-D is an auto- or allo-anti-D.

If the patient was (initially) found to be D Positive, I would again perform a DAT, but would also remember to take into account the ethnic origin of the patient, as it could be a Partial DIII or similar.

[SMILLER 853]

I believe that the bit about  "Determining the phenotype of the autologous red cells is an important part of antibody identification"   has more to do with troublesome rule-outs / rule-ins when trying to determine possible allo-antibody status of the patient..  (eg, if the patient is E antigen pos you do not have to worry about ruling out that antibody).  I am not sure if they meant for this to apply to situations where you have already adequatly ID'd the anitbody, such as an anti-D.

Scott

[Malcolm Needs ★ 4,543]

16 minutes ago, SMILLER said:

I believe that the bit about  "Determining the phenotype of the autologous red cells is an important part of antibody identification"   has more to do with troublesome rule-outs / rule-ins when trying to determine possible allo-antibody status of the patient..  (eg, if the patient is E antigen pos you do not have to worry about ruling out that antibody).  I am not sure if they meant for this to apply to situations where you have already adequatly ID'd the anitbody, such as an anti-D.

Scott

Hmmm, well, as a Reference Laboratory, we ALWAYS typed the red cells, whatever the (apparent) specificity of the antibody, common or rare.

[SMILLER 853]

Except of course, when the patient has been recently transfused or pregnant, antigen typing the patient is a routine part of an antibody workup.  

Cool thing about ref labs, they can do other neat stuff we are unable to accomplish in the trenches, like phenotyping retics and other amazingly useful things for us when needed!

 

Scott

[BankerGirl 197]

I don't see any reason to perform a weak D on a patient with an anti-D as you are going to give Rh negative blood anyway, unless like Malcolm said, the DAT came out positive.  Why do additional testing with no clinical value?  If the patient DOES type positive with Weak D, then I assume you would change the blood type to Rh positive and still need to give negative blood.  Seems to me like that would just be confusing to most folks (clinicians and technologists) for no reason.

[Malcolm Needs ★ 4,543]

30 minutes ago, BankerGirl said:

I don't see any reason to perform a weak D on a patient with an anti-D as you are going to give Rh negative blood anyway, unless like Malcolm said, the DAT came out positive.  Why do additional testing with no clinical value?  If the patient DOES type positive with Weak D, then I assume you would change the blood type to Rh positive and still need to give negative blood.  Seems to me like that would just be confusing to most folks (clinicians and technologists) for no reason.

No, that was not exactly what I was saying.  If the DAT was positive, then it is likely that the "Weak D" test (as performed in the USA) would also be positive, and so you should NOT change the patient's type to D Positive at this stage.  Only after an elution has been made, and anti-D has been identified in that eluate can it be said that the patient is D Positive (assuming that they have not been transfused or pregnant in the previous three months) or it has been proved by molecular techniques that the patient is D Positive.  Once this has been done, then, of course, the patient's type can be changed to D Positive.  If it can be confirmed that the patient is D Positive, and that the anti-D is an auto-antibody, then it is actually quite safe to switch to giving D Positive blood (as it would be to transfuse antigen positive blood whenever an auto-antibody is present, except in exceptional circumstances).

Edited January 23, 2017 by Malcolm Needs

[BankerGirl 197]

Sorry Malcolm, my statement was not clear.  I meant that if the DAT was positive you may not need to give Rh Negative blood, not that you should do a Weak D.  Poor sentence structure, inadequate proofreading.  If the DAT is negative with a positive Weak D reaction, it may NOT be an autoantibody and the patient would need Rh Negative blood.  I think this post makes sense, but I have been having issues with communication lately.  

[Malcolm Needs ★ 4,543]

Thanks BankerGirl.  I'm sure I was not entirely without fault.

[mollyredone 318]

On 1/20/2017 at 9:50 AM, Malcolm Needs said:

Hmmm, well, as a Reference Laboratory, we ALWAYS typed the red cells, whatever the (apparent) specificity of the antibody, common or rare.

 

On 1/21/2017 at 7:28 AM, SMILLER said:

Except of course, when the patient has been recently transfused or pregnant, antigen typing the patient is a routine part of an antibody workup.  

This is why I was confused about the validity of antigen typing a pregnant woman!

[Simon1994 5]

On 1/23/2017 at 8:43 PM, BankerGirl said:

I don't see any reason to perform a weak D on a patient with an anti-D as you are going to give Rh negative blood anyway, unless like Malcolm said, the DAT came out positive.  Why do additional testing with no clinical value?  If the patient DOES type positive with Weak D, then I assume you would change the blood type to Rh positive and still need to give negative blood.  Seems to me like that would just be confusing to most folks (clinicians and technologists) for no reason.

 

I agree with her.

[Mabel Adams 1,060]

If doing a test won't change how you will manage the patient, then I think it is seldom worth doing.  Besides, it will make your computer unhappy and you know how difficult they can be when they are unhappy.