Is There a Definitive Test for Lyme Disease?

Even in winter months, doctors diagnose the tick-borne illness.

Bryan Arling, M.D.

The most sensitive test for Lyme disease is the Western blot, which looks at three IgM antibodies and 9 IgG antibodies to antigens found on the Borrelia bacteria that cause Lyme disease. Two or three positive IgM bands suggest an acute infection, and five or more of the IgG bands suggest an infection at an indeterminate time in the past. It takes several weeks from the time when an infected tick releases the infection into your body for you to begin mounting an antibody response, so a test would be negative at an early stage. Our current blood tests for Lyme disease are 90 percent accurate, and we know that a significant percentage of patients not only lack the bull's-eye rash initially described but lack a rash of any sort.

Some Lyme disease experts recommend treating with doxycycline for three days after removing an embedded tick since this will substantially decrease the likelihood that one would develop Lyme disease even if the tick were carrying the organism. In the Washington area, we have experienced warmer winters and a substantial increase in the deer population, and we diagnose Lyme disease even in the winter months. Some physicians who say they specialize in the treatment of Lyme disease will treat patients with three antibiotics, including intravenous ceftriaxone, for several months even though studies published from academic centers have failed to show that superaggressive treatment improves outcomes.

We have no way of proving that Lyme disease has been fully treated. Antibody tests can remain positive for many months after the organisms have been eradicated. Clinical symptoms may persist because the bacteria live in the small blood vessels that supply nerves and other tissues. If those blood vessels are blocked by the inflammation, patients can continue to experience symptoms long after the last organism has died.

There are other viruses, bacteria, and malaria-like parasites that mimic Lyme disease, so it is not surprising that some patients are overtreated and some are undertreated. If the diagnosis or treatment is in question, an infectious-disease consultation could be very worthwhile.

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