John, I use the term "immunesuppressed" to mean that there is a weak conncentration of ABO Ab and/or alloAb. But you have stated the precise reason for any extended work with a weak backtype, "immunocompromised." This is exactly what we can not understand from our testing methods, if there is indeed a compromise at all; nor can we fully understand the length of the condition either, will it last a few hours,days,weeks, or months. To go and extrapolate this reasoning to all patients irregardless of backtype reactivity is to say that our testing systems are completely invalid, and this is just not true. As far as missing a weak antibody in an immune competant patient, I would ask how are you judging immune competance; certainly not completely by our testing methods, you are also looking at patient history, and current condition and making a judgement call on the relative immune competance of this patient. If your backtype gives strong reactivity why would you even question the immunecompetancy; however if the backtype gives weak reactivity then there is ample reason to question the immunecompetancy because you a tangible results pointing towards immunesuppression; which, as I stated earlier, may not be the only reason, but to produce the better compatible product for this patient we should test on the side of caution.