The need and possible risks of various tests when red rash on the penis

Hello. The problem is this. Not long ago I noticed that on the tip of my penis appear and disappear as small red spots. I went to the doctor and passed blood and a swab of the channel. Later she told me that the blood clean and swab too further said that we should test you for pot planting. The question is: what brings this pot planting do I need to take it if my blood and swab clean? I just do not want again to go through these painful procedures and spend the money how is it different from previous tests ? And of course, what do you think about my symptoms? Thank you

Response: "Hello! They are different tests. Given the lack of 100% methods of diagnosis, it is not always possible to identify a pathogen from one method. A more accurate test is the PCR. In addition, you need to pass the secret of the prostate. I wish you health."