Testing in Lyme Disease
Given that culture of B burgdorferi is difficult to grow and its use is generally limited to research studies, the diagnosis of Lyme disease is typically performed by serologic confirmation. Testing relies on a 2-step approach, with samples that are positive or equivocal by ELISA being tested by Western blot analysis for IgM and/or IgG. The CDC has strict guidelines for the interpretation of Western blot results (≥ 2 of 3 bands positive for IgM and ≥ 5 of 10 bands positive for IgG), and it is known that IgM testing is fraught with false-positive results. Some commercial laboratories use different interpretation criteria than those set by the CDC (eg, examining reactivity to nonstandard proteins and/or requiring a different number of positive bands); testing performed at these centers should be interpreted with caution. Only patients with at least an intermediate pretest probability (eg, not patients presenting with nonspecific pain or fatigue syndromes) should be tested. Even with appropriate antibiotic therapy, patients can remain seropositive for years, potentially confusing the clinical picture if the test is not judiciously used. The use of PCR to detect B burgdorferi DNA in joint fluid is an effective adjunctive test for patients with arthritis. In contrast, PCR testing of CSF lacks sufficient sensitivity to be useful as routine testing for patients with possible neuroborreliosis.
According to guidelines from the Infectious Diseases Society of America, Lyme disease can usually be successfully treated with oral doxycycline except in patients with objective neurologic findings (involving more than Bell palsy) and third-degree atrioventricular block. In patients with a contraindication to doxycycline (eg, younger than 8 years of age), amoxicillin, cefuroxime, and erythromycin represent second-, third-, and fourth-line alternatives. A 14-day course of therapy is typically sufficient for early localized infection; a 21-day antibiotic course is generally recommended for early disseminated infections. Lyme arthritis can be treated with 30 days of oral therapy followed by 28 days of intravenous ceftriaxone in patients who do not respond. For patients with neurologic involvement, 14-28 days of intravenous ceftriaxone is recommended. Patients with third-degree atrioventricular block should initially receive parenteral antibiotic treatment, transitioning to oral antibiotics as their cardiac conduction system normalizes.
Medscape Pediatrics © 2013
Cite this: Recurrent Lyme Disease: Old or New Infection? - Medscape - Oct 21, 2013.