Prewarm Technique

[DebWerner]

Under what conditions do Blood Bankers use a prewarm technique to exclude cold reacting antibodies??  I am looking to restrict the use of this technique to only when indicated but am having trouble coming up with an inclusive list of indications.  Any input would be appreciated.

[Bet'naSBB]

we can only use it with tests that require the addition of anti-IgG - such as an antibody screen or full XM.  we are not allowed to use it for IS testing such as reverse testing or ISXM.

so - in my mind, I'd say it could be used when a patient has a cold-auto ab and you want to see if there are any underlying clin.sig ab's after the addition of anti-IgG 

if our reverse and/or ISXM are positive due to the presence of cold auto - we have to cold adsorb and retest with absorbed plasma.

[exlimey]

I was taught, many, many moons ago, that prewarming should only be applied when the identity/specificity of the antibody is known/understood, i.e., you know what you're trying to avoid. Cold autos are probably the most commonly seen, but "nuisance" cold-reactive antibodies like anti-M, anti-P1, anti-Lea/Leb can also pop up and potentially be avoided using a prewarm version of an assay. These specificities are usually IgM class, are amenable to prewarming, and are generally considered clinically insignificant. Prewarming to "get around them" is often a good option.

However, a cautionary note: There are cold-reactive antibodies that can present in a similar fashion that are clinically important - anti-Vel , anti-PP1Pk, for example. It can be dangerous to use prewarming to avoid these sometimes potent and potentially life-threatening alloantibodies.

Prewarming may be a very useful tool, but as is true for very specialized tools, it should only be used and applied by trained and experienced operators who understand its strengths and weaknesses.

[Malcolm Needs ☆]

3 minutes ago, exlimey said:

I was taught, many, many moons ago, that prewarming should only be applied when the identity/specificity of the antibody is known/understood, i.e., you know what you're trying to avoid. Cold autos are probably the most commonly seen, but "nuisance" cold-reactive antibodies like anti-M, anti-P1, anti-Lea/Leb can also pop up and potentially be avoided using a prewarm version of an assay. These specificities are usually IgM class, are amenable to prewarming, and are generally considered clinically insignificant. Prewarming to "get around them" is often a good option.

However, a cautionary note: There are cold-reactive antibodies that can present in a similar fashion that are clinically important - anti-Vel , anti-PP1Pk, for example. It can be dangerous to use prewarming to avoid these sometimes potent and potentially life-threatening alloantibodies.

Prewarming may be a very useful tool, but as is true for very specialized tools, it should only be used and applied by trained and experienced operators who understand its strengths and weaknesses.

Certainly in the case of an anti-Vel, it can be vital to use serum, rather than plasma, as it can frequently only be detected by using an AHG that detects complement.

I DO SO AGREE WITH YOUR FINAL SENTENCE.

[Neil Blumberg]

We only use it for antibodies that are unlikely to be clinically significant (an example would be anti-M) if they do not react at 37 and antiglobulin phase.  Sometimes you find an anti-M that reacts weakly at 37, but not antiglobulin phase, and the prewarm makes it disappear at 37.  In most cases, we would then ignore the antibody. Just some additional information to make clinical decisions. 

We wouldn't bother for antibodies usually capable of causing red cell destruction at body temperature.  A strong cold with broad thermal amplitude up to 37 would not be much helped by pre-warming, so we use other techniques such as auto-adsorption to make it "go away."  Thus we don't bother there with prewarming, just as we wouldn't be interested in making an anti-C or anti-Jka disappear by prewarming.

Edited May 6 by Neil Blumberg