Using only mixed field anti-D (ortho gel) as qualitative indicator for RhIg eligibility

[JoyDenver]

As a COLA Surveyor I inspect many small rural hospital Blood Banks and I have never run across a procedure like this: "If the post-partum Rh test on the mother is mixed fieldpositive, a sample of the  mother's blood is sent to the reference lab at the blood center for quantiation of the FMH by KB stain".  The Lab uses Ortho gel for their ABORh testing.  I have always thought routine Anti-D reagents are not manufactured for this purpose (detecting FMH) and a Fetal Screen must be performed because the Anti-D in the FS kit is modified and FDA approved to detect smaller quantities of fetal blood that may be in Mom's circulation.  What is the best explaination I can give this Lab to convince them their paractice may be unsafe.

[Malcolm Needs ☆]

I would tell them 1) to read the package insert, which, I bet, does NOT say it can be used for this purpose, and 2) tell them to contact Ortho about this practice, and I bet Ortho will also tell them that they are playing with fire.

I haven't heard anything quite so stupid for a very, very long time.

[Joanne P. Scannell]

I agree:  If the manufacturer must state that this is a valid Fetal Cell Screen OR there must be literature/studies out there validating that a FMH greater than 30mL will always be detected in gel (ABO and Rh Typing).  Has anyone out there seen such literature?

Yes, annoying when facts are twisted and general statements are made that don't reflect the truth of the matter.  There are lots of them out there. 

Grrr, too.

[JoyDenver]

I told the lab just that and they will immediately implement using a fetal screen for their ONeg moms with Rh Pos babies.  It's always a good feeling that I can come into a small rural hospital to educate them on their BB practices to better serve their community. I feel I've done my job as a COLA Accreditation Surveyor!

[John C. Staley]

Let me play the devil's advocate.  I don't see anywhere they are stating that the anit-D is being used to screen for FMH.  As I read it all they are saying is that if the post partum Rh test is mixed field they should send it off for a K-B to make sure it is not due to FMH or if it is to quantify it for them.  I am assuming that the post partum Rh is a test they perform on all deliveries.  So a question I have to ask is do they have a routine method for determining FMH such as a rosette test or are they in fact actually using the routine anti-D testing specifically to determine FMH.  

Hope I wasn't too confusing.

[David Saikin]

My thinking is along the lines of John's.  They are just examining the postpartum Rh type of the mother.

[goodchild]

Read her title for the thread. "Using ONLY mixed field anti-D as qualitative indicator." Sounds like they were trying to do a little cost containment.

[John C. Staley]

I would like to see it in a quote from an SOP and not simply the title of a thread.  We all make assumptions based on limited info.  The quote in the original post did not specify this.  Just looking for a little clarification.

 

 

[R1R2]

This would be horrible, if in fact, they were using the test in lieu of a rosette test.   All I can think about is he possibility that some moms did not get the required amount of RhIG.    

[Eagle Eye]

I think we should not judge anyone without knowing exactly what is their intent?

[Dansket]

There is no such thing as mixed-field in gel testing.  The term mixed-field is used to describe microscopic reading of tube tests.  Gel tests are read macroscopically and use the term 'dual-population'.

[Malcolm Needs ☆]

4 hours ago, Dansket said:

There is no such thing as mixed-field in gel testing.  The term mixed-field is used to describe microscopic reading of tube tests.  Gel tests are read macroscopically and use the term 'dual-population'.

There most certainly is such a thing as a mixed-field reaction in gel testing Dansket.  There are many occasions where a mixed-field will be seen.  For example, in the anti-A column, when group O blood has been given to a group A recipient, in the anti-D column when D Positive blood has been given to a D Negative recipient (or vice versa), when the patient has a D mosaic type (much more common than a lot of people think, often when performing extened typing afyer the patient has been transfused, in a true chimera, after stem cell transplants, etc, etc, etc.

[Dansket]

Malcolm, please re-read my post.  Mixed-field is a term used to describe the observation of a microscopic reading on a slide of the contents of a standard tube test where there may be seen "individual clumps of red cells in sea of unagglutinated red cells".

Two populations of red cells will be present in a group A recipient of a group O red blood cell transfusion.  When testing a post-transfusion blood sample, a band of agglutinated red cells will be trapped at the top of the gel column, a button of red cells will be seen at the bottom of the gel column and no red cells trapped within the anti-A gel column.  These observations are visible without the aid of a magnifying device and are graded as dp  dual-population according to MTS-ID Gel Card Interpretation Guide used for both manual and automated gel testing.

 

 

[Malcolm Needs ☆]

4 hours ago, Dansket said:

Malcolm, please re-read my post.  Mixed-field is a term used to describe the observation of a microscopic reading on a slide of the contents of a standard tube test where there may be seen "individual clumps of red cells in sea of unagglutinated red cells".

Two populations of red cells will be present in a group A recipient of a group O red blood cell transfusion.  When testing a post-transfusion blood sample, a band of agglutinated red cells will be trapped at the top of the gel column, a button of red cells will be seen at the bottom of the gel column and no red cells trapped within the anti-A gel column.  These observations are visible without the aid of a magnifying device and are graded as dp  dual-population according to MTS-ID Gel Card Interpretation Guide used for both manual and automated gel testing.

 

 

Okay Dansket, I accept what you are saying in terms of definition, but I still say that mixed-field reactions can be seen in gel in cases of the A₃ phenotype, D mosaics (see above), many antibodies directed against antigens within the Lutheran Blood Group System, where the stringy appearance of the agglutinates seen in tube agglutination is also seen in gel, and those with anti-Sd^a specificity.

[Dansket]

12 hours ago, Malcolm Needs said:

Okay Dansket, I accept what you are saying in terms of definition, but I still say that mixed-field reactions can be seen in gel in cases of the A₃ phenotype, D mosaics (see above), many antibodies directed against antigens within the Lutheran Blood Group System, where the stringy appearance of the agglutinates seen in tube agglutination is also seen in gel, and those with anti-Sd^a specificity.

I'm not disagreeing that other types of serological phenomena are seen as mixed-field reactions when viewed microscopically on a slide, but can only speculate as to how these reactions are observed in gel.  I've seen A₃ and anti-Sd^a mixed-field reactions through a microscope on a slide but not yet in gel.  I'm curious, have you see an A₃ in gel?

 

 

Edited December 18, 2016 by Dansket
added content

[Malcolm Needs ☆]

Hi Dansket,

Yes, I have seen several examples of the A₃ phenotype, several examples of D mosaic and quite a few Lutheran antibodies of various specificities, all in gel, but not an anti-Sd^a.  It may seem a bit "strange" that I can claim to have seen "several examples" of the A₃ phenotype in gel, but it has to be remembered that we have been using the gel technique for well over 16 years, and that I worked (that past tense still seems really weird!) in one of the two Red Cell Immunohaematology Reference Laboratories in London, which has a huge ethnic mix, and so we saw all sorts of rare antigens and antibodies.

[KKidd]

This was our procedure before FMH kits were available, like 30 years ago.  Glad to have the FMH screen now.

 

[tricore]

1 hour ago, KKidd said:

This was our procedure before FMH kits were available, like 30 years ago.  Glad to have the FMH screen now.

 

I was just sitting here trying to remember what we did before Ortho produced fetal screen.

[Dansket]

7 hours ago, Malcolm Needs said:

Hi Dansket,

Yes, I have seen several examples of the A₃ phenotype, several examples of D mosaic and quite a few Lutheran antibodies of various specificities, all in gel, but not an anti-Sd^a.  It may seem a bit "strange" that I can claim to have seen "several examples" of the A₃ phenotype in gel, but it has to be remembered that we have been using the gel technique for well over 16 years, and that I worked (that past tense still seems really weird!) in one of the two Red Cell Immunohaematology Reference Laboratories in London, which has a huge ethnic mix, and so we saw all sorts of rare antigens and antibodies.

Please describe the appearance of the anti-A gel column when testing an A₃ phenotype?  Was the distribution of red cells in the gel column classic dual-population (rbc trapped on top, rbc button at the bottom, but no rbc within the gel column) or something else?

[Malcolm Needs ☆]

It was, if you like, a mixture of the two.  There was a whole load of red cells trapped at the top of the column (obviously group A), a whole load of red cells as a button at the bottom (apparently group O) and just a few red cells trapped in the column from top to bottom (a bit like the appearance of a Lutheran antibody, but much weaker).

[Mabel Adams]

When the rosette test came out there was literature comparing what volume of FMH could be detected by a microscopic reading of a weak D test on the Rh negative mom's post-delivery sample compared with what could be detected by the rosette test.  I assume the D typing research would have been with the human source anti-D of the era, not current monoclonals and certainly not the gel anti-D. As I recall (from 35 years ago) this value was above the 30 ml of FMH used for the RhIG dosing decisions which is why we all switched to using the rosette test. (Wait, now I remember that we did KBs on every one of these patients for about a year before the commercial rosette kit came out!)  It would be very interesting to know if the modern testing for D, including in gel, could be sensitive enough to pick up excessive FMH reliably.  It would be a great boon to small hospitals.  Sounds like a good SBB student project.  The vendors have no motivation to validate this because they all sell a rosette kit.  Of course, it shouldn't be attempted unless there are data to support the practice--either published or self-validated.

[mollyredone]

Ortho actually describes the dual population as "mixed field" in its interpretation guide and shows pictures of equal amounts of cells on the top and bottom of the tube.  I have a hard time training new techs that a little touch of red at the top is not a mixed field, but trapped fibrin.  Ortho's manual also shows negative results as having a little bit of red cells at the top.

[Mabel Adams]

Yeah, Ortho tried for years to get us not to call it "mixed field" but finally gave in.