Provue Issues

[johna]

There are isolated reports of anti-E and anti-K being missed using a gel antibody screen and I believe that Ortho made a few adjustments in the product a while back which may have solved the problem. Has anyone encountered this problem recently?

Regarding gel titers. Rh antibody titers in gel appear to be significantly enhanced vs. tube testing. Has anyone seen this enhancement with other antibodies (K, FyA, etc.)?

[galvania]

Can't talk for Ortho but the DiaMed gel system is known to be more sensitive that a normal tube technique. It's quite common to get antibodies that titer two, three, four or even more tubes higher in gel than in tube, depending on exactly how the tube test is being carried out, and sometimes even by whom! As for the Coombs gel missing some anti-E, it will certainly miss out clinically insignificant enzyme-only anti-E, but would not normally miss out a real coombs one.

[OPUS104]

We have seen a decent amount of "scratchy" Gel reactions turn into very strong E,K and a very few Fya's. We have ran into this enough that if we get a negative Gel screen on a unit that tested + in a pool with solid phase, then we do a PEG tube screen. The usual difference we see in strength is Gel reactions are stronger than tube by a factor of 2. (1+ tube= 3+ Gel) These missed Gel antibodies are just a typical case of "no testing method will cacth everything". (We are a donor center by the way.)

[santy76]

Dear friends

Can someone let me know how one can determine sensitivity of Gel technique on AHG (Coombs cross match) card. is there any SOP for gel technique, if yes, please mail me on santy76@indiatimes.com. and apart from Diamed which other cards are available to perform gel technique.]

[DMR]

We are new gel manual testing users and are looking for protocols for how OB Titers can be set up in Gel - Do you have any protocols you would be willing to share?

Thanks,

DRose

[Cathy]

We continue to perform antibody titers in tube.

Are the scratchy reactions you refer to newly formed antibodies by any chance? We have found that the antibodies we missed in gel were newly formed and easily picked up with Liss or PEG.

[galvania]

We are new gel manual testing users and are looking for protocols for how OB Titers can be set up in Gel - Do you have any protocols you would be willing to share?

Thanks,

DRose

Hi - the way we titre antibodies on gel in DiaMed is to double dilute the patient's plasma in Diluent 2 (the diluent used to make your cell suspensions) for 12 tubes using volumes of 100ul (can be increased if you want to tritrate against lots of different cells - something we do, but not something many diagnostic labs would need to do very often, I imagine). Then 25ul of each dilution is placed on top of the cells in the coombs cards in the same way as plasma is for an antibody screen.

Best wishes

Anna

[DMR]

What do you mean by double dilute the patient's plasma?

DRose

[galvania]

12 tubes. 1 vol diluent in tubes 2-12. 1 volume plasma to be titrated in tubes 1 and 2. Tube 2 is then at a dilution of 1:2. Mix the contents of tube 2 and, with a clean pipette tip, transfer 1 volume to tube 3. Mix...and so on until the last tube. Does this have another name in american English? It would not be the first time i have had language problems on this site.

[janet]

We did serial dilutions (as galvania described) in gel for a couple years....until we were consistently 2 or more 'tubes' higher in our lab proficiency testing (the Province of Ontario sends out to each licensed lab). The proficiency agency stated that tube IAT testing is considered the "gold standard" so we changed back and follow the AABB Technical Manual method.

[galvania]

We did serial dilutions (as galvania described) in gel for a couple years....until we were consistently 2 or more 'tubes' higher in our lab proficiency testing (the Province of Ontario sends out to each licensed lab). The proficiency agency stated that tube IAT testing is considered the "gold standard" so we changed back and follow the AABB Technical Manual method.

Yes - for most IgG antibodies, the titre in gel is at least 2 tubes higher than in tubes; so obviously if, for example, you are monitoring an ante-natal patient with antibodies and switch from tube to gel half-way through, it is important that whoever is reading the report understands that this is a 'technical' increase in titre and not a 'true' one (if that is the case, of course). But you would expect an increase in titre with a more sensitive method, surely? And they are SO much easier to read.......I wouldn't go back to tube testing for routine work for anything!

[Mabel Adams]

Anna, I think the language issue is a nuance. We might say we did "doubling dilutions" but I hadn't heard the verb form that I can think of--it seemed an understandable extension, so I knew what you meant after a second's thought. Of course, I am an old blood banker who was taught things like ASO titers in school. One of the nice things about this forum is that it is open to us as well as generalists and those from different backgrounds. I enjoy your unique perspective.