I think its the culture, but I am going to let someone else answer for sure. I've asked one of our members with more expertise in this area to respond. :)
I would like to respond. Both of the tests you mention are very accurate. The DNA probe test has better than a 98 percent accuracy. However a positive result from a culture is 100 % specicific. The technique for the culture involves a blind passage from one culture medium to another with MOMP protein staining of the second passage. This is diagnostic nothing else would give a false positive with the culture. Of course the culture would take 1 to 2 weeks to process. The DNA probe is reliable enough. I suggest using the Gen probe swab on penile