I Just Went To The Doctor To Get The Results

I just went to the doctor to get the results of the tests for my yearly check up. He gave me a copy of the test results. Now at home I am checking all the numbers and they are in the normal range, but for one only: leukocyte esterase: 500, hi. The Dr. did not comment on that at all. In the internet I see the normal range should be negative. Should I be concerned? For over a year now I have been having lower back pain and my urinary track feels uncomfortable. Thank you very much for your reply.