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Positive Autocontrol in gel, negative DAT


CMCDCHI
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Maybe my understanding about this question is wrong, because of my not good English and not good professional knowledge. But I still can not stop myself from speaking out my opinion. As usual, corrections are always welcomed.

If the autocontrol is pos, I will do poly then IgG and C3 DAT specifically.

But there are also some pos auto, but neg DAT, then I think there are two kind of situations:

1. the method interference.

2.the auto antibodies are too weak to be tested by DAT, in this circumstance, I prefer to do an elution test.

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Speaking of Poly DAT....

Our current Positive and Negative control for the poly qc is    :

Positive control add 1 drop Poly IgG to one drop of Coombs control spin and read.

For the negative control Add 1 drop of  A1 cells to 2 drops and Anti-D. Incubate tubes for 15 minutes and centrifuge, wash 3 times with saline and add 2 drops of Poly specific coombs reagent. Spin and read    (verbatim)

Our manufactures instructions

Drections for Use

Bring reagent to room temperature (25°C ± 5°C) prior to use.

Direct Antiglobulin Test

1. Prepare a 3% to 5% suspension in isotonic saline of the red blood cells to be tested.

2. With a clean Pasteur pipette, add one drop of the prepared cell suspension to a small test tube.

3. Fill the tube with fresh isotonic saline; centrifuge at high speed and decant. Perform this washing a minimum

of three times.

4. Decant completely after the last washing. (CAUTION: Do not reintroduce human serum components after

washing procedure.)

5. Add two drops of Anti-Human Globulin BioClone.

6. Mix well and centrifuge immediately.

Suggested centrifugation: Approximately 15 seconds at 3400 rpm (900-1000 rcf) or 1 minute at

1000 rpm (100-125 rcf).*

7. Resuspend the red blood cells by gentle agitation and examine immediately for macroscopic agglutination.

8. Examine negative tests with an optical aid

 

 

Do I need to change our procedure?? 

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  • 2 months later...

Suggestion...drop the routine autocontrol. There is no requirement to run it with the antibody screen. If your patient has a positive antibody screen or incompatible crossmatch, then do the auto as part of the antibody ID workup. If the auto is positive, do the DAT. If the DAT is positive, do the differential DAT.

If the auto is positive, but the screen is negative and the crossmatch compatible, what do you do differently to transfuse the patient? Anything? If you aren't changing the transfusion protocol in that case, is there value in performing the test routinely?

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1 hour ago, AMcCord said:

Suggestion...drop the routine autocontrol. There is no requirement to run it with the antibody screen. If your patient has a positive antibody screen or incompatible crossmatch, then do the auto as part of the antibody ID workup. If the auto is positive, do the DAT. If the DAT is positive, do the differential DAT.

If the auto is positive, but the screen is negative and the crossmatch compatible, what do you do differently to transfuse the patient? Anything? If you aren't changing the transfusion protocol in that case, is there value in performing the test routinely?

If this is for me, we are only doing autocontrol's with an antibody panel.  I couldn't imagine doing one with every antibody screen!

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19 hours ago, amym1586 said:

Currently we are doing     Autocontrol in Gel.  If positive--> Poly DAT in tubes.  If positive--> IgG DAT in tubes.  Then mass confusion.   

I don't understood the rationale for using a less sensitive methodology (Tube Test DAT) to invalidate the results of a more sensitive methodology (Gel-DAT).  An auto-control (rbcs+plasma+37C incubation=Indirect Antiglobulin Test) and a DAT (rbcs only - no incubation=Direct Antiglobulin Test) are different tests and I don't expect them to agree 100% of the time (having done gel testing continuously for past 11 years).  Auto-control is not a reportable result.  If the Gel-DAT (anti-IgG card) is positive, I report DAT-Positive regardless of the auto-control results. Just my 2 cents!

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27 minutes ago, Dansket said:

I don't understood the rationale for using a less sensitive methodology (Tube Test DAT) to invalidate the results of a more sensitive methodology (Gel-DAT).  An auto-control (rbcs+plasma+37C incubation=Indirect Antiglobulin Test) and a DAT (rbcs only - no incubation=Direct Antiglobulin Test) are different tests and I don't expect them to agree 100% of the time (having done gel testing continuously for past 11 years).  Auto-control is not a reportable result.  If the Gel-DAT (anti-IgG card) is positive, I report DAT-Positive regardless of the auto-control results. Just my 2 cents!

Oh I understand completely!   I have not been the blood bank supervisor here for very long. They do a few things I do not agree with.  I'm working on so many things but  I hope to get this process fixed.

Edited by amym1586
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29 minutes ago, Dansket said:

I don't understood the rationale for using a less sensitive methodology (Tube Test DAT) to invalidate the results of a more sensitive methodology (Gel-DAT).  An auto-control (rbcs+plasma+37C incubation=Indirect Antiglobulin Test) and a DAT (rbcs only - no incubation=Direct Antiglobulin Test) are different tests and I don't expect them to agree 100% of the time (having done gel testing continuously for past 11 years).  Auto-control is not a reportable result.  If the Gel-DAT (anti-IgG card) is positive, I report DAT-Positive regardless of the auto-control results. Just my 2 cents!

I've meant to ask, how do you handle complement?

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Goodchild,

I don't use the PolyDAT gel card.  In response to a request/need for DAT on adult, I use the anti-IgG card and a buffered gel card.  Liquid anti-complement reagent is added to buffered gel card and incubated 10 minutes with patient rbcs, centrifuge and read.  Results are reported separately for anti-IgG test and anti-complement test. 

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On 5/27/2016 at 8:33 AM, Dansket said:

I don't understood the rationale for using a less sensitive methodology (Tube Test DAT) to invalidate the results of a more sensitive methodology (Gel-DAT).  An auto-control (rbcs+plasma+37C incubation=Indirect Antiglobulin Test) and a DAT (rbcs only - no incubation=Direct Antiglobulin Test) are different tests and I don't expect them to agree 100% of the time (having done gel testing continuously for past 11 years).  Auto-control is not a reportable result.  If the Gel-DAT (anti-IgG card) is positive, I report DAT-Positive regardless of the auto-control results. Just my 2 cents!

I wouldn't be doing a DAT if my auto-control were negative!  Since all we stock is IgG cards, maybe I'll look into buying buffered cards and adding my own complement like you do.  We do tube DATs for hemolytic anemia and 99% of them are negative with poly so we quit right there.  What kind of expiration date do the buffered cards have?

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On 2/25/2016 at 10:59 AM, StevenB said:

First and foremost...if you are going to go back and do a DAT because the AC came up positive, make sure you do it with a freshly made cell suspension.  Also, if taking that step and you have the reagents, test with polyspecific (PS) and IgG at the same time  since you suspect it will be positive.  If you only test with PS and it comes up positive, you'd have to make ANOTHER fresh suspension to test with IgG if you were going to do that.  The 10-12 minutes it takes to do the PS test is too long for cells to sit in suspension for an accurate IgG DAT.

What we do is make a fresh cell suspension and then wash three tubes (one for poly, one for IgG and one for complement) with one drop each.  If the poly is negative and check cells work, we toss the other two tubes.

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Buffered Gel cards have same expiry date as other cards but may not be cost effective for you.  I also use my Buffered Gel cards for Immediate-Spin crossmatch and testing with liquid Anti-A,B (ABO confirm of donor rbc units labeled O POS).

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On 2/26/2016 at 5:43 AM, Malcolm Needs said:

I would certainly do it in gel, but I would use the cards that contain monospecific reagents for anti-IgG, anti-IgM, anti-IgA, anti-C3c and anti-C3d.

Every lab I have worked in in the UK (and I have been around a bit) only do anti-IgG, and anti-C3d and an auto control as that's what is in the cards. Surely this is enough to pull up if it is clinically significant? Or should we be using 6 well instead of 3 well, cards.

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Yes, but don't forget that I work in reference Auntie-D, and so we are more often seeing the unusual.

For example, we have had patients who give all the symptoms of AIHA, but with a negative DAT within a hospital setting, but who have a DAT that is positive by monospecific anti-IgA only.  We have also seen patients with mixed cold and warm AIHA (very rare and complex to diagnose at a laboratory level) that we suspected by the differential DAT results.

I am not, for a single second, suggesting that all hospital laboratories require to have such cards, but we do.

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