Jump to content

Rh Pos or Rh Neg?


Cliff

Recommended Posts

Is that 16% all Rh neg women or just ones with FMH? If it's just FMH patients then the overall number of people developing anti-D would be very low. To conserve Rh negative we often give Rh pos instead to anyone except women in child bearing years and I can think of 1 in the past two or three years that actually made an anti-D. I've seen more anti-E and -K develop than anti-D. Allergies, man. Some people get them on the first dose and some never do after twenty.

Link to comment
Share on other sites

That is all pregnancies, because these figures were determined before anti-D immunoglobulin was available, let alone available as a routine dose during pregnancy.

Darren, can I be really cheeky and ask you to use females of child-bearing potential, rather than women in child-bearing years?  Using the former helps people on the ward and in the laboratory that, say, a ten-year-old D Negative girl would also need D Negative blood, and may also need anti-D immunoglobulin.

Link to comment
Share on other sites

  • 2 months later...

You may be interested in "Strategies to identify candidates for D variant genotyping" by Luo, Keller, et. al. (Blood Transfus 2018; 16: 293-301). Our facility currently uses BioRad Anti-D via tube testing. If an OB patient reacts 1+ or less at immediate spin we send the patient out for Weak D molecular testing. We just got an Ortho Vision, so I am looking at implementing the strategies outlined in the paper to help identify those Weak or Partial D patients.

Link to comment
Share on other sites

After a lot of reading and deliberation, here is what we ended with.

Testing of Male Patients and Female Patients ≥ 56

Interpret according to Rh Tube Test SOP.  Follow discrepancies as outlined for women below, except for sending for molecular testing.

 Testing of Female Patients < 56

  • For newly tested women less than 56, if result is 0, testing is complete. 
  • If > 0 but < 2+, interpret as Rh neg and perform Rh molecular testing.  Notify a supervisor to have molecular testing performed.
  • If ≥ 2+, interpret as Rh pos.

This is for all women less than 56, not just OB patients.

 Discrepancy Resolution

What is a discrepancy?  Let’s keep it simple.  Regardless of what methodology was used for their previous type, if it was interpreted differently than the SOP says to interpret it now, it’s discrepant.  If we get conflicting info from an outside facility, or the patient themselves, it’s discrepant.  Discrepant is defined as: Rh pos when previously resulted as Rh neg, or Rh neg when previously resulted as Rh pos (at BWH, at any other institution, or per patient history.). 

  • For Male Patients and Female Patients ≥ 56, follow the Rh Discrepancies chart in Rh Tube Test SOP.
  • For women < 56 with a discrepant result, interpret as Rh Neg.  Notify a supervisor to have molecular testing performed.
Link to comment
Share on other sites

Cliff I feel your pain about this issue. We have often had to explain this issue with much difficulty to physicians whose patient have a historic RH positive from another facility but we call it negative. And sometimes it is truly negative not calling it negative because the reaction is 1+(that is Legacy's cutoff). I agree with the other panel member(sorry can't remember your name) if we call antibody screens + that are 1+ why don't we call a patient Rh positive if their D is 1+.

Anyway what we have done is explain that RH D testing can change based on the reagent or testing mechanism and that is safer to go with the RHIG injection than not go with the injection but it is ultimately up to them ( of course I don't say this but the pathologist does). We have also (once) sent a sample to the reference lab to see if the D was partial or weak and were able to get the results back within the 72 hours. I don't see us doing this all the time though

Link to comment
Share on other sites

On 1/25/2019 at 10:54 AM, Cliff said:
  • If > 0 but < 2+, interpret as Rh neg and perform Rh molecular testing.  Notify a supervisor to have molecular testing performed.

 

Why interpret it at all until the extended testing is done? It seems this would create confusion among doctors. "It was negative and then it wasn't!"

Link to comment
Share on other sites

2 hours ago, slsmith said:

 I agree with the other panel member(sorry can't remember your name) if we call antibody screens + that are 1+ why don't we call a patient Rh positive if their D is 1+.

 

Remember that 1+, 2+, 3+ and 4+ are test results and that test results may be interpreted accordingly to the test being performed and to the user's protocol for Rh grouping. For example, the ORTHO Gel Anti-D direction insert states that agglutination observed in the anti-D gel column should be interpreted as Rh positive (assuming a negative control test), but some users may interpret weak agglutination ( less than 2+) in Anti-D Gel as Rh negative.

Link to comment
Share on other sites

1 hour ago, Dansket said:

Remember that 1+, 2+, 3+ and 4+ are test results and that test results may be interpreted accordingly to the test being performed and to the user's protocol for Rh grouping. For example, the ORTHO Gel Anti-D direction insert states that agglutination observed in the anti-D gel column should be interpreted as Rh positive (assuming a negative control test), but some users may interpret weak agglutination ( less than 2+) in Anti-D Gel as Rh negative.

Plus we should remember the goal of each test.  In the case of prenatal Rh typing, identifying the patient who should get RhIG to prevent possibly making anti-D whenever possible is the goal, not generating a binary pos/neg answer.  Unfortunately the reagents available aren't perfect for this but we need to be able to defend our decisions to the woman who makes anti-D and never has another healthy pregnancy.

Link to comment
Share on other sites

  • 1 year later...

Sorry I missed this discussion, it was very interesting.  Since an email sent out re-opened this discussion I would just make a brief comment.  HDN is a terrible outcome for the child especially, and also the mother and family.  Not using antenatal RhIg is medical negligence.   Not giving a potential D negative female/mother RhIg is close behind.   It has always been a challenge with our anti-D reagents to deal with interpretation of weak reactivity and females of "child-bearing" age.  And our testing methods have improved over the years.  However, with the advances in molecular biology is serology really the best way to make this life-changing decision?  Should prenatal molecular testing be standard?  

Thank you Mabel Adams for reminding us of one of our most important goals!

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    • No registered users viewing this page.
  • Advertisement

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.