The testing has to be done by someone. This lab has more incentive to give back successful results because of reputation and personal cost.If it is a pathogen, which is easy to find, they will most likely report it. The tricky ones are the chronic stuff; fungi, and protozoa. These are the PPTU
All worms poop, which is easy to ID, at least for me. The labs are unable to qualify this because of licensing regulations. The techs would have a good idea, but cannot report on it.
If you get a PPTU, then it means go the antiparasitic route.