Immucor FMH RapidScreen ABO incompatibility

[labguru]

Mother is O negative, baby is A negative. The DAT on the baby is positive, so the Weak D is inconclusive.

According to the limitations of the FMH screen, if you have a weak d (which we don't know if it is or isn't because of the positive DAT) you must use a test to detect feto-maternal hemorrhage other than the screen. We send out a KB for this determination. However, the limitations also state that "in cases of ABO incompatibility between mother and child, the mother's natural ABO antibodies may destroy any fetal cells in the maternal blood specimen before testing is performed. This is true for any method of detecting fetal cells in the maternal blood."

So my question is would you send this ABO incompatible specimen out for a KB or would you just issue the mother one vial of Rhogam and not worry about the KB since nothing may be detected? This was an uncomplicated vaginal delivery.

[Malcolm Needs ☆]

41 minutes ago, labguru said:

Mother is O negative, baby is A negative. The DAT on the baby is positive, so the Weak D is inconclusive.

According to the limitations of the FMH screen, if you have a weak d (which we don't know if it is or isn't because of the positive DAT) you must use a test to detect feto-maternal hemorrhage other than the screen. We send out a KB for this determination. However, the limitations also state that "in cases of ABO incompatibility between mother and child, the mother's natural ABO antibodies may destroy any fetal cells in the maternal blood specimen before testing is performed. This is true for any method of detecting fetal cells in the maternal blood."

So my question is would you send this ABO incompatible specimen out for a KB or would you just issue the mother one vial of Rhogam and not worry about the KB since nothing may be detected? This was an uncomplicated vaginal delivery.

Without a doubt I would send it for KB, because the operative word in the limitations is "may" - they are not always destroyed.  In addition, even if the delivery was an uncomplicated PV, that does not rule out that there may have been a major, but silent FMH that requires a larger dose of anti-D immunoglobulin than your standard dose.

[R1R2]

agree with Malcolm

[mld123]

We always perform a Fetal Stain if the babies Rh is indeterminate due to a positive DAT.  Agree with above.

[TreeMoss]

Has anyone ever used the FMH RapidScreen test on cord blood to determine the Rh of a baby in this scenario?  Our reference lab suggested that as a possibility, but I've not been able to find any references for this procedure.  If the FMH RapidScreen is negative on cord blood, that should indicate that the baby is Rh negative with a positive DAT.  If the FMH RapidScreen is positive, that should indicate that the baby is Rh positive.  Positive DAT does not affect the FMH RapidScreen test.  Curious to know your thoughts.

[kate murphy]

Well, think about this... the indicator cells are rosetting any cell with IgM coating it  - test uses a monoclonal IgM anti-D.  But anything else that's IgM coating the cells may give you pos test. 

You cannot tell with certainty using this test the Rh of the baby.  Certainly it's not the test of record.  If you ever had to defend your result, you'd have difficulty. 

Picture this:  you've presumed the baby is Rh neg based on the FMH screen.  No RhIG for mom.  Baby is really Rh pos (variant?), and mom goes on to develop an anti-D.  Next baby is at risk.  Mom sues.  You have no defense, as this is not standard practice. 

In the case of a pos DAT with an inconclusive Du, we do a KB and presume the baby is Rh pos.  RhIG dose based on the KB.

[Carrie Easley]

We perform a gentle heat elution.  If we successfully attain a negative DAT after the elution, we test baby for weak D.

[TreeMoss]

We also currently do the Kleihauer-Betke stain on moms with weak D positive babies to determine whether they need more than one 300 mcg dose of RhIG.  We also let them know that they may return to the lab in 6 months, if they would like, to have the blood type of the baby rechecked.  No one has taken us up on that offer yet, but we would like to have a verification of the baby's blood type, if possible.

[AMcCord]

On 12/27/2016 at 0:39 PM, TreeMoss said:

We also let them know that they may return to the lab in 6 months, if they would like, to have the blood type of the baby rechecked.  No one has taken us up on that offer yet, but we would like to have a verification of the baby's blood type, if possible.

We've had pediatricians reorder a capillary blood type the very next day...even after we've explained to them, in detail, why we can't give them an Rh type on the newborn. I have yet to get a request months down the road for a retype.

[Malcolm Needs ☆]

42 minutes ago, AMcCord said:

We've had pediatricians reorder a capillary blood type the very next day...even after we've explained to them, in detail, why we can't give them an Rh type on the newborn. I have yet to get a request months down the road for a retype.

They ALWAYS know better, don't they!  Depressing.

[gagpinks]

On 20/12/2016 at 3:06 PM, Malcolm Needs said:

Without a doubt I would send it for KB, because the operative word in the limitations is "may" - they are not always destroyed.  In addition, even if the delivery was an uncomplicated PV, that does not rule out that there may have been a major, but silent FMH that requires a larger dose of anti-D immunoglobulin than your standard dose.

If baby is Rh Negative why do need to perform FMH test. In this case, do you think positive DAT could be due to ABO incompatible or antibody against low frequency antigen? Or something I am not aware of. 

It might be silly question  but why would you perform weak D typing if baby is Rh neg. 

[labguru]

3 minutes ago, gagpinks said:

If baby is Rh Negative why do need to perform FMH test. In this case, do you think positive DAT could be due to ABO incompatible or antibody against low frequency antigen? Or something I am not aware of. 

It might be silly question  but why would you perform weak D typing if baby is Rh neg. 

 

According to the limitations of the FMH screen, if you have a weak d (which we don't know if it is or isn't because of the positive DAT) you must use a test to detect feto-maternal hemorrhage other than the screen.

You only know if it is a weak D if you do the weak D testing on an Rh Negative specimen and when you add the Anti-IGG it will show up in this patient as positive due to the DAT. I think the positive DAT was due to the ABO incompatibility.

We perform a weak D on all our Rh negative cord bloods to determine if the mother needs RHIG.

[gagpinks]

17 minutes ago, labguru said:

 

We perform a weak D on all our Rh negative cord bloods to determine if the mother needs RHIG.

Now it make sense but in uk we don't perform weak D typing on cord sample. What method do you use to perform your blood group?  We use gel technology to perform blood group on cord sample unless weak reaction with anti-D 

Edited January 23, 2017 by gagpinks

[labguru]

3 minutes ago, gagpinks said:

Now it make sense but in uk we don't perform weak D typing on cord sample. What method do you use to perform your blood group?  We use gel technology to perform blood group on cord sample.

We use Ortho Gel for the Blood Group, and tube for the weak D.

[Malcolm Needs ☆]

17 hours ago, gagpinks said:

If baby is Rh Negative why do need to perform FMH test. In this case, do you think positive DAT could be due to ABO incompatible or antibody against low frequency antigen? Or something I am not aware of. 

It might be silly question  but why would you perform weak D typing if baby is Rh neg. 

The baby has not been proved to be D Negative, as the DAT is positive.  Until the cause of the DAT is fully understood (you are correct in saying that it could be as a result of an ABO incompatibility, or an antibody directed against a low prevalence antigen, but it could equally be anti-D, or a combination of any of these causes), or that the baby is expressing a weak or Partial D, which cannot be proved or disproved while the DAT remains positive.  Under such circumstances, the mother should be offered anti-D immunoglobulin (as a belt and braces exercise), and if the offer of anti-D immunoglobulin is accepted by the mother, you are duty bound to make certain that the standard dose is sufficient.  If this is not sufficient, a calculation should be performed to ensure that a sufficient dose is given.

THERE IS NO ROOM OR EXCUSE FOR GUESSING IN ANY AREA OF BLOOD TRANSFUSION.

[AMcCord]

21 minutes ago, Malcolm Needs said:

THERE IS NO ROOM OR EXCUSE FOR GUESSING IN ANY AREA OF BLOOD TRANSFUSION.