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Negative Control for DAT


ebjjwilson

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Our facility performs negative control with all DATs.  We also use Check Cells in all negative patients AND the negative control.  Does anyone else put CC in the negative control?  Is it required or necessary since it will always be negative?

Edited by ebjjwilson
clerical
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  • 2 weeks later...

None of the institutions I have have worked for have added check cells to the DAT control - the check cells should be QC'd as part of daily reagent QC. From my point of view, since no AHG is added to the DAT control, the check cells serve no purpose. For negative Poly, Anti-IgG, and Anti-C3 DATs we did add check cells to verify that those reagents were not neutralized by free IgG or complement. 

Edited by Lucky Jack
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3 hours ago, Lucky Jack said:

None of the institutions I have have worked for have added check cells to the DAT control - the check cells should be QC'd as part of daily reagent QC. From my point of view, since no AHG is added to the DAT control, the check cells serve no purpose. For negative Poly, Anti-IgG, and Anti-C3 DATs we did add check cells to verify that those reagents were not neutralized by free IgG or complement. 

Please excuse my ignorance, but how can a "DAT Control" not have an antiglobulin reagent?

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I thought the purpose of the Check cell was to verify that the AHG reagent was "working" and had not been inactivated at some point during the test, giving a false negative result. If this verification isn't performed,  how do you know that it isn't negative because the reagent was inactivated?

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On 2/22/2018 at 10:49 AM, ebjjwilson said:

Our facility performs negative control with all DATs.  We also use Check Cells in all negative patients AND the negative control.  Does anyone else put CC in the negative control?  Is it required or necessary since it will always be negative?

Is your patient DAT control simply 2 drops saline added to patient cells? If so, then adding check cells is not necessary.

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sounds like your negative control is really not controlling anything.  If you are using antiglobulin reagents then you should be adding them to you negative control and expect a reaction with check cells.  If you qc your reagent daily there should be no reason to run a negative control with each test (i.e., you've tested the reagents with a positive and negative system).  For my C-3b,-C3d testing I run my A2 cell as the negative control of the antisera;  C3 sensitized cells are the pos control, run w the antisera.  I do this testing in gel.

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2 hours ago, David Saikin said:

sounds like your negative control is really not controlling anything.  If you are using antiglobulin reagents then you should be adding them to you negative control and expect a reaction with check cells.  If you qc your reagent daily there should be no reason to run a negative control with each test (i.e., you've tested the reagents with a positive and negative system).  For my C-3b,-C3d testing I run my A2 cell as the negative control of the antisera;  C3 sensitized cells are the pos control, run w the antisera.  I do this testing in gel.

David taught me this!  We switched to gel for both IgG and complement DAT and use the buffered cards for complement and require QC with every patient test to verify that the anti-sera was actually added, using A2 cells and complement check cells.

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23 hours ago, AMcCord said:

Is your DAT control simply 2 drops saline added to patient cells? If so, then adding check cells is not necessary.

If you are talking about the patient saline control, rather than a control for the Anti-AHG reagent, then check cells are not necessary.

From a package insert......"False-positive reactions in the direct antiglobulin test may be recognized by carrying out a control test on each red blood cell suspension tested, in which two drops of saline are added at step 3, instead of Anti-Human Globulin. The control will facilitate the recognition of aggregates caused by Wharton's Jelly, or of aggluutinates produced by 'complete' (IgM) autoantibodies that have not dissociated during the washing phases."

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  • 1 month later...

Daily QC shows that the Poly, anti-IgG, anti-C3b,-C3d, CC and CCC reagents are working correctly and negative reactions at the AHG phase show the cell washer is removing free IgG/IgM.

My understanding is that the DAT negative saline control is only required when the patient has a positive poly, IgG and compliment DAT. The DAT saline control, when negative, rules out pollyagglutination (either microbial or acquired). Therefore if the patient's Poly or anti-IgG or anti-C3b,-C3d DAT is negative; pollyagglutination is ruled out and the saline control is not needed.

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4 hours ago, Ensis01 said:

My understanding is that the DAT negative saline control is only required when the patient has a positive poly, IgG and compliment DAT. The DAT saline control, when negative, rules out pollyagglutination (either microbial or acquired). Therefore if the patient's Poly or anti-IgG or anti-C3b,-C3d DAT is negative; pollyagglutination is ruled out and the saline control is not needed.

Polyagglutination (one L) is a phenomenon demonstrated by some red cells in the presence of most normal human sera. It has little to do with a positive DAT. Perhaps you mean "spontaneous" or "non-specific" agglutination ?

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16 hours ago, exlimey said:

Polyagglutination (one L) is a phenomenon demonstrated by some red cells in the presence of most normal human sera. It has little to do with a positive DAT. Perhaps you mean "spontaneous" or "non-specific" agglutination ?

My apologies you are correct, monoclonal reagents rule out polyagglutination in the DAT (Isset, Harmening and Daniels) and I should have said:  "Therefore if the patient's Poly or anti-IgG or anti-C3b,-C3d DAT is negative; false positive results are ruled out and the saline control is not needed."

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