Pinning down the Lyme disease antibody.

Pinning down the Lyme disease antibody

Half the people with Lyme disease fail to show its characteristic red rash, which makes diagnosing it difficult. Worse, some of these people don't test positive for the disorder on standard diagnostic tests, which detect antibodies to the bacterium Borrelia burgdorferi, the cause of Lyme disease that infects people through the bite of a tick.

Researchers now report they apparently have found the cause of he negative tests in infected people: antibodies to the disease often completely bind to antigens on B. Burgdorferi and routine testing doesn't detect them, says Patricia K. Coyle of the University of New York at Stony Brook, co-author of the report published in the Feb. 10 LANCET. In most infectious diseases, extra, unbound antibodies circulate in the blood and can be detected by a laboratory test.

The researchers analyzed blood samples from 10 subjects who had symptoms of the disease, including the rash, but had negative antibody tests. They found that all 10 patients ahd bound antigen-antibody complexes. The researchers used a laboratory test that split apart the antigen-antibody complex, releasing the bound antibody so it could be detected. Coyle says this may one day become a routine second test for people with Lyme disease symptoms but negative antibody tests.

The researchers used three control groups to confirm their findings: 21 of 22 subjects who tested positive for the disease also had the antigen-antibody complex; all 19 controls with other diseases did not have the complex, and four of 12 controls with no rash but with other symptoms, and who tested negative for the disease, had the antigen-antibody complex. Apparently the other eight either weren't infected or had such low antibody levels that they couldn't be detected yet, Coyle says.