False Negative Reasons :
Some of the reasons why the worst cases of infection will always tend to test "negative" has to do with the nature of the blood test itself.
The tests that are predominantly used are designed to test for the antibodies that fight against the lyme organism—the spirochete. Antibodies are substances that the body itself produces in response to an infection. In short, when an infection enters the body, the body produces antibodies to fight against it, overwhelm it, and destroy it..
Well, in the case of the severe lyme infection, the quantity of infecting spirochetes is so high, there are not enough antibodies to go around, leaving none of them available to be tested for in the common blood tests.
A second type of blood test (called PCR) is accurate—in a sense. This test seeks to find the specific DNA of the lyme organism. A positive result in this test is assuredly a confirmation that there is the presence of the lyme spirochete. However, the nature of this test is it's problem (and the test is expensive, too): The problem is, as an image, like scooping a cup into a swimming pool, and hoping to come up with the single cotton ball that's floating around in the pool. There's just too little organism to be found.
Our own US Center for Disease Control states plainly that the blood tests are too inaccurate, and the diagnosis for lyme is to be "clinical" -- by the symptoms.
Bottom line? And the reason for writing all of this — Don't rely on blood tests alone. Understand the danger if your doc is trying to tell you that "since you have negative blood tests," you categorically "have no lyme."
Correct lyme diagnosis is a clinical one.