Hi!

This might be a stupid question but I need some feed back from you guys. Do you perform daily qc on your IgG cards for DAT. If yes then what qc material do you use. The reason why I'm asking for your opinion is because we are in debate if it is necessary to really do a DAT qc on an IgG card that we daily qc using our commercially prepared antisera. For me, if you base it by just the reagent being tested I would say NO because it is the same gel card (IgG) but if you base it on methodology and the type of qc reagent (check cells vs antisera) then we do need to do a separate qc. So what do you guys think?

 

 

You need to do positive/negative controls for anti-IgG cards for every day of use. This can be direct or indirect.

 

If you perform DATs in gel, you also need a positive/negative control for the diluent for every day of use.

I think your daily QC would cover an IgG+DAT = you are detecting a cell coated with IgG regardless of the source.  I run my diluent as a negative control - this covers both the cells and the diluent.  If the negative control reacts then either my diluent or my cells are compromised. 

 

I run the monospecific anti-C3b,-C3d (and the IgG card).  When I run the complement test I run the comp+ cell and I run the patient with diluent as a check.  If my anti-comp DAT is positive I also run a negative ct on my antisera (2x in the last 10 yrs).

I got my QC plan from someone on the forum. Each morning I run the MTS diluent with A2 cells for my negative and IgG check cells for my positive. This tests the MTS buffer as well as IgG for gel DATs.

We run positive/negative controls for both Antibody Screen and IgG DAT on ProVue.  The results demonstrate that the Anti-IgG gel card detects coated rbcs by both direct and indirect antiglobulin testing methods.

We do a saline negative control with our tube DATs.  The Ortho gel DAT procedure does not list a comparable negative control for doing IgG DATs in gel.  Will autoagglutination never cause a false positive in a gel DAT?  How about Wharton's jelly causing interference?

 

10 hours ago, Mabel Adams said:

Will autoagglutination never cause a false positive in a gel DAT?

 

Auto-agglutination, particularly with a "cold reacting" auto-antibody of wide thermal amplitude will often cause a kind of false positive in that, as well as the expected reactions with anti-IgM and/or anti-C3d monospecific reagents, we often saw reactions with the anti-IgG, anti-IgA and anti-C3c monospecific reagents, and the negative control.  We could almost always get around this by washing the red cells with pre-warmed saline, prior to adding the red cells to the cassette.

We wash our cells 4 times for DAT.  We only do it 4 times because that is where our cell washer is set and we wash babies 4 times.

We use our Ortho check cells made to 0.8% as our positive control and the 0.8% Ortho screening cells for the negative control every day a DAT is done.

Like ANORRIS, we use a 0.8% made of Check cells for pos control and one screen cell from Ortho screening cells (we make it up from the 3% to save our 0.8%) as the negative. Day of use. We also use these for the IgG-C3d cards, in addition to a C3d positive control.

 

So no one doing Gel DATs is running the equivalent of a saline control to make sure that the patient's cells aren't autoagglutinating and causing a false positive?  A decade or so back this became an expected part of the tube DAT test, at least if the patient's DAT was positive in all tubes run.  I am hoping to learn whether the equivalent of a saline control is not expected in gel DATs and, if not, why not.  Malcolm, we don't have any AHG cards but IgG (and a poly card is the only other one available for MTS in the US).

Mari, does your cell washer manage washing cell suspensions okay?  Some are designed only for washing a cell button.  Is it a Helmer UltraCW?

Mabel,  I just looked at the AABB technical manual and it states that if both the IgG and Complement DATs are positive, you should perform a saline or albumin control.  We have only had one DAT for hemolytic anemia in the last six months (27 samples) that was positive for both and we had to send it out due to a warm auto.  We use the buffered gel card for our complement and run controls with each patient or run to make sure we have remembered to add the anti-C3b, -C3d reagent.

We use Helmer UltraCW and add 3-4 drops of packed red cells, and then 10 microL in 1 mL of MTS diluent.  We have only had one problem that I can recall, and that was with a cord blood and I just washed it a few more times.

It depends what you have available.  Here  there are 'Coombs' cards (either poly or just IgG) for doing the DAT; most of the time a positive result would then be tested on a card that differentiates between IgG and complement or IgG, IgA, IgM and complement.  Both of these two cards have a control on them which is the equivalent to your 'saline control'.  I too have seen some lovely cold agglutinin disease samples that are positive across the board, saline control included