Negative DAT qc

[LaraT23]

Is anyone using albumin for negative qc for DAT? The previous super wrote in to the policy that the 22% albumin we use should be diluted to 6% before we use in for QC? Any reference?

[NedB]

Negative tests are not required by CAP and AABB. You must test the 'reactivity' of your reagents. Running a 'Negative' DAT would seem to prove nothing.

[LaraT23]

Well in the DAT procedure in the tech manual, it states that if the results with all antisera are pos, the test must be repeated. That means to me that there should be one that is expected not to agglutinate, hence the negative control. I cannot find any reference for how to do that though.

[NedB]

Our protocol is that daily when we use the QC kit (Ortho's and Immucor's are similar) we take the tube with Anti-D and the AB- cell to Anti-IgG and the check cell. This also satisfies the NERL Blood Bank saline requirement of doing a DAT daily. On testing a Patient for DAT we include a reagent cell to test with the Anti-C3b,-C3d. We have settled on using the A1 reverse typing cell. I can see the temptation to add 6% albumin to test the adequacy of the washing; but that is the purpose of the check cells which you must use anyway.

[galvania]

Lara, do you mean that if you have a patient whose DAT is positive and you then check it out with anti-IgG and anti-C3d, or whatever, and both of those are positive, then you want a negative control to prove that in fact, your patient has not agglutinated (due to cold aggs) before his cells actually hit the coombs reagent? If that is what you mean, then your negative control must depend on what's in your monospecific Coombs reagents. The control should contain everything that the Coombs reagent contains, with the exception of the antibody. This controls not only the cold aggs scenario, but also non-specific reactions due to components of the buffer. In the ID cards all the Coombs monospecific cards come with a control well just for this purpose. You should talk to your manufacturer; they should be able to point you in the right direction

[bbbirder]

If your concern is primarily cold agglutinins, I would think a saline check after washing the cells would work.

Linda Frederick

[LaraT23]

I did find on the net recommendations for using 6% albumin to mimic the low protein environment of the monoclonal reagent. I did not find however what might be the problem if you do not use a low protein.

I was also wondering about doing DAT in gel, there is not recommended qc other than that of the gel itself that we do in the mornings. Seems if you do one, you do the other???

[Lcsmrz]

I follow the recommendations in the product insert: saline cell control for Anti-IgG and 6% Alb cell control for Anti-C3

[Kathy3171]

For our negative DAT QC we use blood bank saline.

Edited August 27, 2008 by Kathy3171