Posted February 12, 20214 yr comment_81571 "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.
February 13, 20214 yr comment_81574 How about the DAT of this donor? Edited February 13, 20214 yr by yan xia
February 13, 20214 yr Author comment_81575 On 2/12/2021 at 4:55 PM, yan xia said: How about the DAT of this donor? No DAT. There are no other details to the question. I’m just trying to get people’s opinion on the question. Thank you Edited December 5, 20222 yr by SbbPerson
February 13, 20214 yr comment_81576 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 February 13, 20214 yr by Malcolm Needs
February 13, 20214 yr comment_81579 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?
February 13, 20214 yr comment_81580 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!
February 14, 20214 yr comment_81590 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.
February 14, 20214 yr Author comment_81591 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. 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 February 14, 20214 yr by diplomatic_scarf spelling and grammar
February 15, 20214 yr comment_81593 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.
February 16, 20214 yr comment_81600 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.
February 16, 20214 yr comment_81601 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.
February 16, 20214 yr comment_81602 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.
February 16, 20214 yr comment_81603 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.).
February 16, 20214 yr comment_81604 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)
February 16, 20214 yr Author comment_81605 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
February 17, 20214 yr comment_81606 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.
February 17, 20214 yr comment_81607 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
February 17, 20214 yr comment_81608 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.
February 17, 20214 yr comment_81609 Sadly, I can't open the attachment of the answer. I was hoping to see what was considered "critical thinking". From the responses of others it would appear I am not missing much. Carry on folks.
February 17, 20214 yr comment_81610 Hope this works for you John, but you are correct; you were not missing much!
February 17, 20214 yr Author comment_81612 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/
February 18, 20214 yr comment_81617 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.
February 18, 20214 yr Author comment_81620 5 hours ago, David Saikin said: Yes, but DVI donors need to be typed as D+. Donors are not patients. Yes, I know. I was talking about patients on my original post.
February 19, 20214 yr comment_81626 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.
February 19, 20214 yr Author comment_81631 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. https://labs-inc.org/pdf/361_3.pdf
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