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Does this blood bank "critical thinking" question makes sense to anyone?


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"A donor unit obtained from a central blood bank was labeled as Group O, D-negative. When the hospital transfusion service confirmed the donor's type, the result was group O, D-positive. Investigation of the label issued at the blood bank verified the unit's correct labeling. How can you explain the discrepancy in the D type of this donor unit?" 

 

The person who wrote this question said it is a "critical thinking" question and there is only one correct answer.  

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6 hours ago, yan xia said:

How about the DAT of this donor?:)

 

No DAT. There are no other details to the question. Also DATs are not required testing for blood donations. 
 

 I’m just trying to get people’s opinion on the question. Personally I think it is a poorly written question and the person who wrote it has no clue what he’s talking about, but I’m here to get people’s thoughts on it. Thank you 

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Perhaps the monoclonal anti-D reagents had been taken out of the fridge, and not allowed to come to room temperature before being used.  Most, if not all, monoclonal anti-D grouping reagents will detect an I-like or i-like antigen on D Negative red cells (see Thorpe SJ, Boult CE, Stevenson FK, Scott ML, Sutherland J, Spellerberg MB, Natvig JB, Thompson KM.  Cold agglutinin activity is common among human monoclonal IgM Rh system antibodies using the V4-34 heavy chain variable gene segment.  Transfusion 1997; 37: 1111-1116, and Thorpe SJ, Ball C, Fox B, Thompson KM, Thorpe R, Bristow A.  Anti-D and anti-i activities are inseparable in V4-34-encoded monoclonal anti-D: the same framework 1 residues are required for both activities.  Transfusion 2008; 48: 930-940).

What it should NOT be, under any circumstances, is that the anti-D reagents at the Central Blood Bank fails to detect an epitope that is detected by the hospital's anti-D reagent.

Edited by Malcolm Needs
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Malcolm's answer seems reasonable but I'm with you that all the original question does for me is lead to more questions and no answer.  Such as; what does "Investigation of the label issued at the blood bank verified the unit's correct labeling." actually mean??  Was this a real case or just something someone made up?

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43 minutes ago, John C. Staley said:

Malcolm's answer seems reasonable but I'm with you that all the original question does for me is lead to more questions and no answer.  Such as; what does "Investigation of the label issued at the blood bank verified the unit's correct labeling." actually mean??  Was this a real case or just something someone made up?

Thanks, but I would almost guarantee the original question setter hadn't read either of the two papers that I cited!

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I would also like to see the definition of critical thinking used by the original question setter.  That might help trying to understand what they were getting at.  I know from past question writing experience for students, that an answer which I considered so blindingly obvious was in fact not anything of the sort. 

:coffeecup:

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5 hours ago, John C. Staley said:

I would also like to see the definition of critical thinking used by the original question setter.  That might help trying to understand what they were getting at.  I know from past question writing experience for students, that an answer which I considered so blindingly obvious was in fact not anything of the sort. 

:coffeecup:

Yes, I don't think the original question setter meant the question to be a difficult one to answer. He is teaching a beginner level MLT course. He said there was only one correct "straight forward" answer. Just my opinion , but I think this person has no business teaching college level blood banking. As far as I know, he is a MLT with no experience with the tube, slide, or microplate testing methods, so I highly doubt he was talking about Anti-D reagents being the source of the discrepancy. But I could be wrong.

I apologize for wasting people's time with this. I just can't understand how is he teaching medical lab science and blood banking at a local college, and handing out assignments with these sort of questions.   

 

 

Edited by diplomatic_scarf
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15 hours ago, diplomatic_scarf said:

I apologize for wasting people's time with this. I just can't understand how is he teaching medical lab science and blood banking at a local college, and handing out assignments with these sort of questions.   

Please don't apologise; I found your question (your question - not the question) quite stimulating.  I totally agree with your opinion re the question setter.

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Not sure about just one answer - We had a labeled Rh negative RBC from the ARC that retyped as Rh positive.  Upon investigation, it was found the Immucor anti-D reagent we use for retyping had anti-Crawford while the ARC automated process for D typing used an Ortho reagent which was from a different clone.  Not very unlikely but certainly more than one answer.    

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2 hours ago, David Saikin said:

The donor could be a DVI but the blood center is testing using an anti-D that does not detect that epitope  (usually the hospital transfusion service doesn't want to find that person as Rh+ but the donor center does).  OR, the blood center has typed the incorrect unit.

I sincerely hope not David.  If this was donor blood, they most certainly SHOULD use an anti-D reagent that detects a Partial DVI, as such individual's have been known to stimulate the production of anti-D.  If it was a patient, then I would agree with you.

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2 hours ago, Johnv said:

Not sure about just one answer - We had a labeled Rh negative RBC from the ARC that retyped as Rh positive.  Upon investigation, it was found the Immucor anti-D reagent we use for retyping had anti-Crawford while the ARC automated process for D typing used an Ortho reagent which was from a different clone.  Not very unlikely but certainly more than one answer.    

I have ABSOLUTELY no doubt that there is more than one answer!  That having been said, the Crawford antigen is encoded by the RHCE gene, specifically RHCE*ceCF (I'm sure you knew this already - but for those who didn't), and is not D Positive (for anyone interested in a damn good read, see Flegel WA, Wagner FF, Chen Q, Schlanser G, Frame T, Westhoff CM, Moulds MK.  The RHCE allele ceCF: the molecular basis of Crawford (RH43).  Transfusion 2006; 46: 1334-1342.  doi: 10.1111/j.1537-2995.2006.00901.x.).

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1 hour ago, Malcolm Needs said:

I sincerely hope not David.  If this was donor blood, they most certainly SHOULD use an anti-D reagent that detects a Partial DVI, as such individual's have been known to stimulate the production of anti-D.  If it was a patient, then I would agree with you.

Me too.  I have a DVI patient here  (has anti-D and anti-Jka)

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2 hours ago, David Saikin said:

Me too.  I have a DVI patient here  (has anti-D and anti-Jka)

I think most modern Anti-D reagents won't detect DVI and these patients will test as D-negative.  This is probably the answer. Anyways, this is the answer he gave his students.  To me, the answer looks as vague as the question. Not "straight forward" at all. 

 

IMG_2756.heic

 

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14 hours ago, diplomatic_scarf said:

I think most modern Anti-D reagents won't detect DVI and these patients will test as D-negative.  This is probably the answer. Anyways, this is the answer he gave his students.  To me, the answer looks as vague as the question. Not "straight forward" at all. 

 

IMG_2756.heic 2.45 MB · 4 downloads

 

Anti-D reagents are specifically formulated to detect DVI - that is REQUIRED by the FDA in the USA. It was also true of the human sera-based reagents I manufactured in the UK during the 1980s.

There was a period when anti-D reagents were approved for donors or patients. The reagents used for donors were required to detect DVI, arguably the "weakest" expression of the D antigen of the known D-variant and typically that meant an antiglobulin phase was required. Those reagents formulated for patients often were not designed to detect DVI (had no IAT) and subscribed to the "it's better to treat them as D-" philosophy.

Today's reagents are typically qualified/licensed for patients and donors, i.e., they are formulated with the same performance characteristics. Even so, all are a blend of monoclonals (IgM/IgG) since not one single clone can detect all of the "normal variants" (a great oxymoron).

Apologies for some of the antiquated terminology.

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of course it could just simply be that the hospital lab made an error grouping it as a false positive.  As this is a question designed for new students, I doubt whether the level of scientific understanding required is very high at this stage.  It would depend what theory the students had done up until the point that the question was set

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16 hours ago, diplomatic_scarf said:

I think most modern Anti-D reagents won't detect DVI and these patients will test as D-negative.  This is probably the answer. Anyways, this is the answer he gave his students.  To me, the answer looks as vague as the question. Not "straight forward" at all. 

 

IMG_2756.heic 2.45 MB · 8 downloads

 

I agree.  The answer provided is vague in the extreme, and of little or no use to students who are at a basic level.  At that stage in their lives, the "model answer" provided would serve to confuse, rather than explain.

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8 hours ago, exlimey said:

Anti-D reagents are specifically formulated to detect DVI - that is REQUIRED by the FDA in the USA. It was also true of the human sera-based reagents I manufactured in the UK during the 1980s.

There was a period when anti-D reagents were approved for donors or patients. The reagents used for donors were required to detect DVI, arguably the "weakest" expression of the D antigen of the known D-variant and typically that meant an antiglobulin phase was required. Those reagents formulated for patients often were not designed to detect DVI (had no IAT) and subscribed to the "it's better to treat them as D-" philosophy.

Today's reagents are typically qualified/licensed for patients and donors, i.e., they are formulated with the same performance characteristics. Even so, all are a blend of monoclonals (IgM/IgG) since not one single clone can detect all of the "normal variants" (a great oxymoron).

Apologies for some of the antiquated terminology.

"Modern anti-D reagents, while they are very good at detecting weaker forms of the D antigen, are specifically designed to NOT detect the most common form of partial D in Caucasians (DVI, or “D six”), so most Caucasian partial D patients will test as D-negative." -BloodBank Guy 

 

https://www.bbguy.org/education/glossary/glp04/

 

 

 

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18 hours ago, diplomatic_scarf said:

"Modern anti-D reagents, while they are very good at detecting weaker forms of the D antigen, are specifically designed to NOT detect the most common form of partial D in Caucasians (DVI, or “D six”), so most Caucasian partial D patients will test as D-negative." -BloodBank Guy 

 

https://www.bbguy.org/education/glossary/glp04/

 

 

 

Yes, but DVI donors need to be typed as D+.  Donors are not patients.

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On 2/17/2021 at 3:43 PM, diplomatic_scarf said:

"Modern anti-D reagents, while they are very good at detecting weaker forms of the D antigen, are specifically designed to NOT detect the most common form of partial D in Caucasians (DVI, or “D six”), so most Caucasian partial D patients will test as D-negative." -BloodBank Guy 

 

https://www.bbguy.org/education/glossary/glp04/

 

 

 

I disagree. It is in the FDA's manufacturing requirements that DVI be detected. Unfortunately, I couldn't find a suitable CFR quote, but several of the Directions for Use I looked at from different manufacturers indicate that they detect DVI.

However, I agree that strategic differential use of reagents such as these on patients vs donors can certainly help the transfusionist and/or determine the necessity for Rh Immune globulin.

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6 hours ago, exlimey said:

I disagree. It is in the FDA's manufacturing requirements that DVI be detected. Unfortunately, I couldn't find a suitable CFR quote, but several of the Directions for Use I looked at from different manufacturers indicate that they detect DVI.

However, I agree that strategic differential use of reagents such as these on patients vs donors can certainly help the transfusionist and/or determine the necessity for Rh Immune globulin.

 

I disagree. Most gel cards and Anti-D reagents won't detect DVI for patients. Fortunately I can find numerous suitable quotes, because it's true. 

 

download

 

 

https://labs-inc.org/pdf/361_3.pdf

 

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