Serologic Testing in Lyme Disease

Topic Overview: How should a clinician employ serologic tests in a Lyme disease evaluation? Before ordering an ELISA or Western blot the clinician should develop a clinical impression of the patient, taking into account the exposure history, symptoms and exam findings. If Lyme disease is judged to be a diagnostic possibility then testing is reasonable. Neither ELISA nor Western blot testing is sensitive enough to rule out Lyme disease. Because positive ELISA results require confirmation with a Western blot, one can make the case for eliminating the test altogether. Positive Western blots can confirm the clinical diagnosis of Lyme but, in and of themselves, they do not necessarily indicate that a patient is actively infected. In summary, serologic testing does not offer a reliable laboratory “shortcut” to the diagnosis of Lyme disease; Lyme disease remains a clinical diagnosis.