Lyme disease is a multisystem disorder caused by the spirochete Borrelia burgdorferi. It is transmitted by the bite of tiny deer ticks, which reside on deer and other wild animals. Lyme disease is present worldwide, but certain geographic areas show higher incidences. Transmission to humans is highest during the spring, summer, and early fall months. The tick bite usually produces a characteristic rash, termed erythema chronicum migrans. If untreated, sequelae lead to serious joint, cardiac, and central nervous system (CNS) symptoms.
Serologic testing for antibodies to Lyme disease includes enzyme-linked immunosorbent assay (ELISA) and Western blot analysis. Antibody formation takes place in the following manner: Immunoglobulin M (IgM) is detected 3–4 weeks after Lyme disease onset, peaks at 6–8 weeks after onset, and then gradually disappears. Immunoglobulin G (IgG) is detected 2–3 months after infection and may remain elevated for years. Current CDC recommendations for the serologic diagnosis of Lyme disease are to screen with a polyvalent ELISA (IgG and IgM) and to perform supplemental testing (Western blot) on all equivocal and positive ELISA results.
Western blot assays for antibodies to B. burgdorferi are supplemental rather than confirmatory because their specificity is less than optimal, particularly for detecting IgM. 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 criterion for diagnosis.
Collect a 7-mL blood serum sample in a red-topped tube. CSF may also be used for the test.
Observe standard precautions.
Label the specimen with the patient’s name, date, and tests ordered and place in a biohazard bag.
Ten proteins are useful in the serodiagnosis of Lyme disease. Positive blots are:
IgM: two of three of the following bands: 21/25, 39, and 41
IgG: five of the following bands: 18, 21/25, 28, 30, 39, 41, 45, 58, 66, and 93
Serologic tests lack the degree of sensitivity, specificity, and standardization necessary for diagnosis in the absence of clinical history. The antigen detection assay for bacterial proteins is of limited value in early stages of disease.
In patients presenting with a clinical picture of Lyme disease, negative serologic tests are inconclusive during the first month of infection.
Repeat paired testing should be performed if borderline values are reported.
The CDC states that the best clinical marker for Lyme disease is the initial erythema migrans rash, which occurs in 70%–80% of patients.
CDC laboratory criteria for the diagnosis of Lyme disease include the following factors:
Isolation of B. burgdorferi from a clinical specimen
IgM and IgG antibodies in blood or CSF
Paired acute and convalescent blood samples showing significant antibody response to B. burgdorferi
Pretest Patient Care
Assess patient’s clinical history, exposure risk, and knowledge regarding the test. Explain test purpose and procedure as well as possible follow-up testing.
Follow guidelines in Chapter 1 for safe, effective, informed pretest care.
Posttest Patient Care
Review test results; report and record findings. Modify the nursing care plan as needed. Explain the need for possible follow-up treatment and testing to monitor response to antibiotic therapy.
Unlike other diseases, people do not develop resistance to Lyme disease after infection and may continue to be at high risk, especially if they live, work, or recreate in areas where Lyme disease is present.
If Lyme disease has been ruled out, further testing may include Babesia microti, a parasite transmitted to humans by a tick bite. Symptoms include loss of appetite, fever, sweats, muscle pain, nausea, vomiting, and headaches.
Follow guidelines in Chapter 1 for safe, effective, informed posttest care.