The urine test is preferably done before you are on abx. It is often administered after what is referred to as an "abx challenge" or a few days or a week of certain abx. The reason is the way the test works.
The test is detecting dead sprirochetes or pieces of them in the urine. The organism has been known to "hang out" in the bladder. After the antibiotic has been taken for a specified amount of time, the specimen is collected and tested for the dead organisms.
It was the blood test that came back positive. This was after being on Biaxin/Septra for 2 months.
There is NO test which can absolutely rule out Lyme. The most frequently performed test, the ELISA, misses over 60% of cases. The more accurate test, the Western Blot, is still not completely reliable and is generally only given if you have a positive ELISA. Which makes no sense at all but there you have it. So in other words a negative test does NOT always mean that you don't have Lyme. For this reason, the CDC states that Lyme is supposed to be a clinical diagnosis with the test used to help confirm.
Some reasons why a test can come back negative in a Lyme infected patient:
1. The sample was taken too soon after infection for your immune system to have mounted a defense.
2. You are producing a detectable level of antibodies, but the lab made an error.
3. You are producing antibodies to a strain of Borrelia burgdorfiri (Lyme) that the lab cannot detect (for the record, there are over 200 strains in the US alone)
4. You are producing antibodies, but they are bound to they Lyme bacteria (called a complexed antibody) without enough free-floating antibodies in the bloodsteam to be detectable.
5. Your immune system is compromised and not responding properly.
6. By taking antibiotics early in the disease, the immune response may have been aborted.
7. The bacterium has changed its makeup and the immune system hasn't noticed it.
8. The bacterium is cloaking itself inside an immune system cell thereby escaping detection.
9. You have a genetic predisposition to produce a negative test, as shown by Drs. Wang and Hilton in their 2001 publication.
In the largest Lyme disease trial ever conducted (for the Lyme disease vaccine trial for Lymerix) which included 10,000 participants, it was found that 36% of the volunteers with proven Lyme disease (culture or DNA positive) never developed a positive Western Blot.