A 35-year-old man with a positive Lyme test result from a private laboratory

Are the patient’s symptoms consistent with Lyme disease?

Lyme disease is the most common vector-borne infection in North America1,2 and incidence in Canada is increasing, with more than 500 cases reported in 2013.3 However, this patient is very unlikely to have Lyme disease because he lacks both a compatible epidemiologic exposure and clinical findings of Lyme infection.

The cause of Lyme disease, Borrelia burgdorferi, is transmitted to humans through the bite of infected blacklegged ticks (Ixodes scapularis or Ixodes pacificus).1 Most infections occur during spring and summer, and transmission is uncommon if tick attachment is less than 36 hours.1 Infected ticks have now established endemic populations in several Canadian provinces, including British Columbia, Manitoba, Ontario, Quebec and Maritime provinces.3

The signs and symptoms of Lyme disease are categorized into three stages (Box 1).1 Untreated Lyme disease may progress to later stages of infection.1 The term “chronic Lyme disease” is sometimes used to describe a number of later stage syndromes, but lacks a consistent definition. It is occasionally applied to cases in which patients have late neurologic Lyme disease — neuroborrelosis — but such patients have active infection and fall within stage 3. Similarly, some patients with untreated Lyme arthritis will have symptoms for months or years, but are also classified in stage 3.4 A subset of patients with confirmed and appropriately treated Lyme disease will have persistent symptoms beyond six months in the absence of objective clinical findings, which is termed post–Lyme disease syndrome.1,4

Should antimicrobial therapy be offered to this patient?

Treatment recommendations for Lyme disease are outlined in the IDSA guideline1 and vary with the stage of infection. This patient does not have objective clinical evidence of early Lyme infection (i.e., erythema migrans), which is the only stage of infection that should be treated empirically. In all other cases of suspected Lyme disease, infection should be documented with serology based on standardized testing protocols before any treatment is started. Antimicrobial therapy should not be offered to patients with chronic subjective symptoms but negative serology results from a public health laboratory, such as this patient.1 Symptoms may persist for months or years after appropriate treatment in patients with post–Lyme disease syndrome. However, evidence from randomized controlled trials has shown that prolonged antibiotic therapy is associated with no or minimal benefit and increased adverse events in these patients.1,4

The case revisited

This patient has not resided in a Lyme endemic area and lacks objective clinical or validated laboratory findings of Lyme infection. He should be counselled that the methods used by the private laboratory are nonstandardized and may lack the appropriate reliability and validity to establish a diagnosis, and that the testing method used in public health laboratories is the current accepted standard. Antimicrobial therapy is not recommended and could potentially lead to adverse events, including Clostridium difficile infection and vascular catheter-associated complications (were the patient to receive antimicrobial agents intravenously). If there had been a history of potential Lyme exposure in the last four to six weeks, testing at a public health laboratory could be repeated to look for convalescent serology; otherwise, the patient should undergo evaluation for alternative causes for his symptoms.