@joanng, A current test is the only way to know for sure about having mac or any other kind of infection. Remember we are prone to pseudomonas, aspergillus, and other bugs as well. You really cannot gauge whether or not you are infected by the continuance of your antibiotics. I tested negative for mac in 2014, but stayed on antibiotics (not the Big 3) for 6 more yrs as a preventative. I just went off of my meds this past Spring. I do think that you getting another lab test done was a good idea. Even if it is not mac, psuedomonas can sneak up on you as well. It is good to stay on top of things.