Most are clinically diagnosis. If a EM rash (bulls-eye) appears, that is considered a full-proof dx. Prob is, only 30% of people ever get that EM rash.
The test for Lyme, which is the Elisa, has a 93% failure rate. The western blot is more accurate, but most MD's won't order the WB without the Elisa being +
Igenex has the most sensitive testing for Lyme. They follow the CDC's criteria for Lyme bands on testing.
83% of all cases are clinically dx though. It's tough to dx since the bacteria attacks different parts of the body and goes into cyst (bio films) forms
Any Doc can order the testing, but true, most MD's are not familiar with symptoms and cannot dx it. There are LLMD's (Lyme Literate MD's) who are trained to dx. I dx it, but I still send them to their MD to get testing.
It's close to impossible to get a full proof dx from bloods. The EM rash or a + West blot is the only way for a full proof dx.
Is someone comes to me and says they recall a tick bite and then got sick, but never went to see a doc, then I know it's become chronic.
Newly infected Lyme is not an issue. It's cured with 10 weeks of doxy (not the 4 weeks ILADS says) but when it's not caught, it goes into chronic stages and one can live for years with it while it destroys the body.