Lume Disease Serology

Lyme disease is a multisystem disorder characterized by dermatologic, neurologic, cardiac, and rheumatic manifestations in various stages. Epidemiologic and serologic studies implicate a common tickborne spirochete, Borrelia burgdoiferi, as the causative agent.

Serologic tests are able to identify 50% of patients with early-stage Lyme disease and all patients with later complications of carditis, neuritis, and arthritis or who are in remission. The test uses one of three methods: Western blot test, enzyme-linked immunosorbent assay (ELISA), or indirect immunofluorescent assay.

ELISA is used as a screening test for identification of infection or past exposure. The Western blot test for immunoglobulin (lgG) antibody and the indirect immunofluorescent assay for IgM antibodies to B. burgdorferi are automatically performed to confirm reactive ELISA results greater than 1.0 index.

Purpose

• To confirm a diagnosis of Lyme disease

Patient preparation

• Explain to the patient that this test helps determine whether his symptoms are caused by Lyme disease.
• Instruct the patient to fast for 12 hours before the sample is drawn but to drink fluids as usual.
• Tell the patient that the test requires a blood sample and who will perform the venipuncture and when.
• Reassure him that although he may experience transient discomfort from the needle puncture and the tourniquet, collecting the sample takes less than 3 minutes.

Procedure and posttest care

• Perform a venipuncture, and collect the sample in a 7-ml red-top tube.
• If a hematoma develops at the venipuncture site, apply warm soaks.

Precautions

• Handle the specimen carefully to prevent hemolysis.
• Send the specimen to the laboratory immediately.

Reference values

Normal serum values are nonreactive for the ELISA method; the index is less than 1.0. Normal results for the Western blot test are negative for IgM; IgG of less than or equal to 4 bands is nonconfirmatory. Normal titer for the indirect immunofluorescent assay is less than 1:256.

Abnormal findings

A positive Lyme serology can help confirm diagnosis but isn't definitive. Other treponemal diseases and high rheumatoid factor titers can cause false-positive results. More than 15% of patients with Lyme disease fail to develop antibodies.

Interfering factors

• High serum lipid levels (possible inaccurate results, requiring repetition of the test after a period of restricted fat intake)
• Samples contaminated with other bacteria (possible false-positive)
• Hemolysis due to rough handling of the sample
• Failure to observe pretest restrictions