Navigating testing in lyme disease and the approach I use for most patients (as of fall 2016)
Testing is a changing field in lyme disease, with the advent of increased awareness about the condition in general and recently the more ready availability of different testing methodologies from a variety of labs.
The basics of testing that I wrote about many many years ago here still apply, but for many patients there is a basic relatively cost-effective approach that can be utilized. First and foremost, if lyme disease is suspected, other conditions should be evaluated for and ruled out, and in this type of setting, if other tests are negative, we should remember that if lyme is highly suspected we do not have to rely on testing for therapy. An example might be classic patient who had increased exposure to a tick, had mild flu like symptoms, then over the months developed migratory arthritis, night sweats, pain in soles of feet, impaired cognition, air hunger, etc. In such a patient if all testing is negative, including lyme testing, but the history and exam suggest such a group of infections, a discussion of risk vs benefit should happen and then a trial of 6 weeks of treatment would be my approach.
Back to the testing...
The usual testing for lyme disease in the conventional world is two tiered testing. This, in my opinion, has many limitations in terms of missing many patients. At any rate, it is testing for antibodies against lyme. Anibodies are proteins the immune system makes against foreign structures, including lyme and associated infections. They are classified as humoral immunity and come from B cells. The combination of an ELISA, or IFA and then a western blot is done. In these tests, we indirectly test for lyme by seeing if there are any antibodies in our blood that react with whatever strain of lyme the lab is using. That part is bolded because it really spells out the difference between labs. Most if not all CDC labs will use the B31 strain of lyme, whereas other labs will use that plus another strain or more lyme proteins, depending on the lab. The latter do this to try and increase sensitivity, or likelihood of picking up exposure to the infection. There is also interpretation criteria with this type of testing. For example, CDC would consider an IgG western blot positive if there are at least 5 bands (or antibodies) against a group of selective lyme proteins exists. 4 doesn't count. Other labs will use their own criteria and say perhaps two are needed, depending on how specific the protein is against lyme. (Research does support the latter - see Zoller et al where even just a 41 kda antibody, if very strong, was very specific against lyme... published in the 90s!)