Weak QC for IgG gel cards

[frenchie]

Happy lab week everyone!

I am trying to make a weak anti-D dilution so I can get a weak to a 2+ reaction with IgG gel card and screening cells I and II. This dilution is very unstable, even frozen. I am curious to see what others are using?

Thanks!

 

[Malcolm Needs ☆]

We use a genuine weakly reacting anti-D.

[exlimey]

If you are using a commercial anti-D reagent as your starting material, you might be creating your own problems. Most reagents are now monoclonal and as such they often have very peculiar formulations (additives, diluents, etc.) that ensure their stability. When end users dilute or otherwise modify the reagents, they may lose the key element required for reactivity and/or stability (even when frozen).

I suggest you try a polyclonal (human) source (which is probably what Malcolm's group is using). If you need to dilute it to get to the desired reactivity, I recommend using either inert normal human serum or 6% BSA. Both diluents should maximize your chances of stability, either in the liquid state or frozen.

[Dansket]

I use a commercially available QC package containing anti-c and anti-D that reacts 3-4+ with my screening cells.  Almost all of the positive antibody screens that we detect react <3+. So I'm not concerned about detecting weakly reactive patient antibody given that Gel eliminates many of the variables associated with tube testing that can result in failure to detect weakly reactive patient antibody.

[sbazel]

First I make a 1:1000 dilution of Anti-D with 22% BSA, I use the earliest exp. date of the BSA or Anti-D as the dilution exp. date.  This gives a 2+ in my LISS tube method.  Using negative patient plasma I make a 1:10 dilution of the 1:1000.  This gives me a good 2+ in gel.  I give this a 30 day exp and usually get good stability. 

[exlimey]

sbazel - bad idea to use the earliest expiration date of the components of your cocktail. Neither apply to your working reagent. Certainly the anti-D has been grossly modified from its original. To assign a genuine expiration date to your cocktail, you would be obliged to perform a formal stability protocol.

[David Saikin]

I use a commercial qc reagent antibody diluted 1:10 for antibody screens.  QC my panels with the same antibody diluted 1:20.  There is no requirement (in the USA) for your qc antibody to react 1-2+, the standard (CAP) now says 1+ or greater.