eacam58

1.  Complex policy difficult for generalists to remember over time - easy to miss one that "should have been done"
2.  Hard to remember why a Fetal screen may be "very" positive when they no longer remember much about Rh neg (weak D positive).
 
I can relate to the above comments.  Everyone in my lab is a generalist.  They work hard and do their best but it's easy to forget.  I didn't understand weak and partial D until recently.  (I think I understand now!)
 
Fortunately we are small and there are not many of us so I can contact everyone with a weak-D policy in-service/mini-lecture.  
 
Some may feel this is a waste of testing - but it isn't very many pts anymore anyway and I would just rather "know" about these pts up front anyway.
 
I would rather know about these patients too...

I have a question about reporting 1+ or 2+ Rh reactions on the Provue as Rh positive.  
 
Page 4 of the 2005 AABB “Guidelines for Prenatal and Perinatal Immunohematology” states:    "Only when prenatal tests for Rh are unequivocal and clearly reactive (=/>2+) should the woman be considered Rh-positive.”
 
Dr. Joe Chaffin, The Blood Bank Guy, also states a similar opinion in his excellent podcast "Weak in the D's".  Here is a link to his podcast:
 
http://www.bbguy.org/podcast/1012/1012podcast.asp
 
The podcast is 41 minutes long, and if you don't have 41 minutes, skip to 34.12 minutes into the podcast.  That's where he starts talking about OB patients.  At 35.30 minutes into the podcast, he says that transfusion services should consider a lower threshold of positivity for calling Rh negatives--some places call a 1+ reaction or lower in tube testing Rh negative and a 2+ reaction or lower in gel testing Rh negative.  The risk here is giving Rh negative blood when Rh positive blood can be given, but calling these weak Rh reactions Rh negative lowers the risk of immunizing the patient.
 
I am interested in this because last week I realized I didn't have a weak D policy, except that we only perform weak D testing on cord bloods if the mom and baby test Rh negative. 
 
Last week we reported an OB patient as Rh negative, using tube testing with Ortho anti-D bioclone.  The patient's physician informed us that the patient was determined to be Rh positive 2 years ago when the patient had her first child.  I called the lab that performed that testing and found it was a 1+ reaction on the Echo Galileo.  The lab reported that the patient was “Rh Positive by Weak-D test (formerly Du).  RhoGam is not indicated for this patient”.  
 
We use the Ortho MTS gel cards for ABO/Rh testing (manual method) as well as tube testing with Ortho reagents, so we repeated the patient's testing using the gel method, and saw a 1+ reaction for the Rh.  When we performed the tube weak D test, we also saw a 1+ reaction. 
 
(An aside--we are a small lab, performing about 100 type and screens per month, about 40 crossmatches per month, 10 cord bloods per month.  I have been trying to phase the MTS ABD Reverse cards out.  The tube method is more versatile, it is faster in emergencies and according to a cost analysis I did, the tube method is ½ the price of the gel ABO/Rh method.  However, the lab is staffed with generalists, and I have been told it’s better for generalists to use the gel method—no chance of forgetting to add the reagent and more consistency.  We perform antibody screens using the gel method because it is more sensitive (although I realize the gel antibody screen method has its pitfalls such as being a LISS method and possibly missing anti-E and anti-K sometimes, etc.)
 
Anyway, I have come to realize that I need to write a weak-D policy, and I am thinking of including these points: 
Perform weak D testing only on cord bloods when mom and baby are Rh negative, on Rh negative moms when the FMH screen suggests the mom may be weak D positive, and when investigating discrepancies such as the OB patient last week. Calling Rh results less than 2+ in gel and less than 1+ in tube, Rh negative. When the Rh results are less than 2+ in gel and less than 1+ in tube, reporting the Rh as negative and including a comment that indicates the Rh type is weak and atypical and if the patient is a blood donor, the patient would be considered Rh positive, but if the patient is an OB patient or a recipient, the patient should be considered Rh negative. There is a CBBS posting about when the AABB changed the weak D regulations in 2002.  Dr. Judd is quoted as saying that, when it was decided in 2002 that weak D testing was no longer needed to be performed on OB patients, all of a sudden, patients that had been D positive, were suddenly D negative, and this was in the same facility.  Dr. Judd is quoted as saying that these patients were informed of their options...that is, where previously they were D positive and did not require RhIG, they were now D negative, and they could opt to receive RhIG or not...they needed to sign a form.......I hope I remember that correctly....
 
I would like opinions!
 
Thank you!
 
Catherine