Gel Poly DAT vs Tube Poly DAT

[MOBB]

We're correlating gel and tube poly DAT. All of our 2+ or less reactions in gel were negative in tube. I'm worried that if we test in tube, we'll miss things we don't want to miss.

Do most blood banks assume they are junk or not clinically significant? Otherwise, it seems odd that so many hospitals just do tube for poly.

[David Saikin]

I have found that gel reactions of 2+ or less are invariably negative with tubes.  Tubes are still the standard for testing.  What I find bothersome is that folks will use tube IgG testing to f/u a polygel +DAT.  Why would you reflex to a less sensitive method is beyond me. I can see doing a tube poly DAT and reflexing to gel.

I would not be concerned testing in tubes.  I think it boils down to the comfort level of your Medical Director.

[MOBB]

7 hours ago, David Saikin said:

I have found that gel reactions of 2+ or less are invariably negative with tubes.  Tubes are still the standard for testing.  What I find bothersome is that folks will use tube IgG testing to f/u a polygel +DAT.  Why would you reflex to a less sensitive method is beyond me. I can see doing a tube poly DAT and reflexing to gel.

I would not be concerned testing in tubes.  I think it boils down to the comfort level of your Medical Director.

David,

Thank you so much for your reply. I have seen that 2+ in gel are also usually negative in tube. I've been amazed at the number of patients that have changed Rh types and since we've switched gel manufacturers we've had at least one patient/month change from A to A2 and B to A2B pos, each one confirmed by our IRL. 

That's so weird that someone would f/u with a less sensitive method. Has anyone ever explained why to you? I had a very frustrated employee who works in another blood bank tell me that they will repeat a positive polygel DAT in poly tube to try to make it negative and that blew my mind too. 

All this brings me back to my original concern, I may be missing clinically significant reactions in tube.

This is hopefully a temporary switch until Ortho can fill my backorders. We are kicking around the idea of running tube poly along side gel IgG to ensure we don't miss something. However, this could cause confusion when reporting a negative poly with a positive IgG.