J, regarding Lyme disease diagnosis -- it's a clinical assessment. That said, the doctors in this country are trained differently than in other parts of the world.
Way too much credence is given to poor quality tests that utilize the CDC tracking criteria (not diagnostic). Most labs don't regionalize their test assays to the 300+ strains of Borrelia, even fewer test for co-infections. In fact, most ticks (even non-deer ticks) carry Lyme and other bugs (bacteria, viruses, protozoa, etc.). This is well-documented in the literature and in my interviews with scientists across the US. E.g., see the one with Eva Sapi
here.
One of the better blood testing labs accounts for all of these shortcomings:
Welcome to IGeneX, Inc.
There are others, but these guys have been doing it for years. They've been beat up by the various skeptics who wield great influence and power, but they've helped many patients and doctors and are CLIA certified.