Somewhere before I think I have seen ROC used as a method of evaluating the success of validating a microarray experiment via qPCR. It seems like this could work, if you view the PCR results as a source of true positives/true negatives. That's not necessarily the case though, and so I have some reservations about apply ROC in such a manner. Does it make sense to use it that way? I typically just look at correlations between the array and the qPCR results, but AUC from ROC would similarly be a nice summary statistic.