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The Challenge of Diagnosing Lyme Disease

July 29, 2019

From The New York Times:

Lyme disease is on the rise. The 30,000 cases reported annually to the Centers for Disease Control and Prevention by state health departments represent only a fraction of the cases diagnosed and treated around the country. About half the cases occur in people under the age of 21, and boys from 5 to 9 years old are the most commonly affected group, possibly because they spend a good deal of time outdoors.

A recent article in The New York Times about a child who was treated for Lyme disease and did well, offering a reassuring message about relatively straightforward cases of the infection, drew more than 700 reader comments, many of them angrily denouncing the author and predicting medical complications to come for her son. Some responses reflect the frustrations of people who feel they have struggled for years with persistent and recalcitrant symptoms from the infection.

The condition can be challenging to treat, in part because it is not always easy to get the diagnosis right the first time around. The biggest problem is that there is no reliable biomarker for Lyme, no way to test, unequivocally, for the presence of the bacteria, Borrelia burgdorferi, which are transmitted by tick bite and cause the disease.

You can make a diagnosis of acute Lyme disease by seeing the characteristic rash, erythema migrans, which at its most classic looks like a target. But it doesn't always look like that, and it can be hidden in the hair, and it doesn't show up nearly as clearly on darker-skinned people. "A large number of affected patients don't have the rash," said Dr. Lise Nigrovic, a pediatric emergency physician at Boston Children's Hospital.

The blood tests we have don't test directly for the bacteria, but instead test for the body's antibody response. When you hear people talk about sending a "Lyme test" or a "Lyme titer," what they are sending is a two-tiered test, looking to see whether the body is making antibodies to that bacteria. For that reason, the test will be negative early on during the infection, because it takes time for the immune system to mount this defense.

So the Lyme test is not helpful in the earliest stages of infection -- which is when you would ideally like to start treatment. Not only that, it takes a while to get the results.

"For me as an emergency room physician, none of the tests come back in rapid enough time to make a decision," Dr. Nigrovic said. She makes treatment decisions on the basis of symptoms, such as meningitis or swollen joints, she said, and that also means deciding how aggressively to pursue alternative diagnoses -- for example, deciding whether a swollen knee needs to be surgically drained or looking for other possible infections: "In my world, it's like, O.K., do I tap the knee, let the orthopedist take the kid to the O.R. when it's probably just Lyme?"

And the increase in Lyme should remind us that ticks can carry other infections as well.

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