Geographic spread of the ticks that most often cause Lyme disease in the United States and a rise in incidence of bites, resulting in 476,000 new US cases a year, have increased the chances that physicians who have never encountered a patient with Lyme disease will see their first cases.
“It’s increasing in areas where it was not seen before,” Steven E. Schutzer, MD, with the Department of Medicine, Rutgers New Jersey Medical School, Newark, said in an interview. Dr. Schutzer coauthored a report on diagnosing and treating Lyme disease with Patricia K. Coyle, MD, Department of Neurology, Renaissance School of Medicine at Stony Brook University, Stony Brook, New York.
The report, a Curbside Consult published in New England Journal of Medicine Evidence, comes amid high season for Lyme disease. Bites from an ixodid (hard shield) tick — almost always the source of the disease in the United States — are most common from April through October.
Identifying the Bite
About 70%-90% of the time, Lyme disease will be signaled by erythema migrans (EM) or lesion expanding from the tick bite site, the authors wrote. The “classic” presentation looks like a bullseye, but most of the time the skin will show a variation of that, the authors noted.
“The presence of EM is considered the best clinical diagnostic marker for Lyme disease,” they wrote.
Other dermatologic conditions, however, can complicate diagnosis: “EM mimickers include contact dermatitis, other arthropod bites, fixed drug eruptions, granuloma annulare, cellulitis, dermatophytosis, and systemic lupus erythematosus,” they wrote.
Testing Steps
“The current recommendation is to do two-step testing almost simultaneously,” Dr. Schutzer said in an interview. The first, he said, is an ELISA (enzyme-linked immunosorbent assay)-type test and the second one, used for years, has been a pictoral view of a Western immunoblot showing which antigens of the Lyme bacteria, Borrelia burgdorferi, the antibodies are reacting to.
However, the pictoral view is subjective and some of the antigens could be cross-reactive. So the U.S. Food and Drug Administration (FDA) “has been allowing newer substitutes like a second ELISA-like assay that often uses more recombinant, less cross-reactive antigen targets,” he said. The authors advised that, “The second-tier test should not be performed alone without the first tier.”
Dr. Schutzer advised physicians to check with the lab they plan to use before sending samples.
“If you’re a practicing physician and you know you’re using a particular laboratory, you should familiarize yourself with them, talking to one of the clinical pathologists involved in advance to know what the limitations are.” Take the time to talk with the person overseeing the test and get tips on how they want the sample transported and how the cases should be reported, he said.
If the patient has neurological symptoms, he said, before treating talk with a neurologist who can advise whether, for instance, a spinal tap is in order or whether an emergency department visit is appropriate.
“If you just start proceeding you may mess up the diagnostic signs that could show up in a lab test. Don’t be hesitant to ask for extra input from colleagues,” Dr. Schutzer said.