||***REFLEX: Lyme, Western Blot (LYWB2) performed if positive.
|Test Performed Stat
Borrelia burgdorferi is a spirochete that causes Lyme disease. Ticks of the genus Ixodes transmit the organism. In endemic areas, these ticks are commonly found on vegetation, and animals such as deer, mice, dogs, horses and birds. It is characterized by a distinctive skin lesion, systemic symptoms, oligoarthritis, and neurologic and cardiac involvement occurring in varying combinations over a period of months to years.
The illness typically begins in the summer and the usual first manifestation, erythema migrans (EM) develops around the tick bite in 60% to 80% of patients. Within weeks to months after onset of the EM lesion, neurologic abnormalities may develop; symptoms fluctuate and may last for months or may become chronic. Cardiac abnormalities may occur within a few weeks after onset of EM. Weeks to years after onset, swelling and pain in large joints, especially the knees, may develop and recur for several years.
Diagnosis is currently based on clinical findings and serologic tests leading to variable results. Serologic tests are insensitive during the first several weeks of infection and may remain negative in persons treated early with antibiotics. Test sensitivity increases markedly when patients progress to later stages of the disease. Cross-reacting antibodies may cause false-positive reactions in patients with syphilis or relapsing fever. The mode of transmission is tick-borne; transmission does not occur until the tick has fed for several hours. The incubation period for EM is from 3-32 days after tick exposure. However, the early stages of the disease may be asymptomatic and the patient may present with later manifestations of the illness. There is no evidence of natural transmission from person to person.
In 1994, the Second National Conference on Serological diagnosis of Lyme disease recommended a two-step testing system toward standardizing laboratory serologic testing for B. burgdorferi. In accordance with this recommendation, all positive and equivocal results from this method (first step) are further tested by Western Blot (second step). Two-step positive results provide supportive evidence of exposure to B. burgdorferi, which could support a clinical diagnosis of Lyme disease, but should not be used as a sole criterion for diagnosis.