I am not sure what TFT is, so if you could explain. You might consider using Dr. Stensvold's lab in Sweden (or close to it). He is considered one of the best in terms of parasite identification and they can test for rogue bacteria as well. He offers PCR but can do microscopy for much cheaper.
parasite testing is notoriously difficult and for me it required multiple tests and this is true in many cases. PW Labs found the culprit.
The other route is to carpet bomb using strategies for parasites, protozoa, bacteria etc. These would all be different strategies and you use combinations of products that are not widely discussed on these forums. Send me a pm if you need further information.