What is the interpretation of a 2-tiered Lyme disease test?

From the Guidelines

A 2-tiered Lyme disease test is interpreted as positive only when both tiers show reactive results, with the first tier using an enzyme immunoassay (EIA) or immunofluorescence assay (IFA) and the second tier using a Western blot to confirm the results, as recommended by current guidelines 1. The first tier of the test screens for antibodies against Borrelia burgdorferi, the bacterium causing Lyme disease. If this initial test is negative, no further testing is needed and Lyme disease is unlikely. If the first test is positive or equivocal, the second tier test, a Western blot, is performed to confirm the results. For a complete positive diagnosis, the Western blot must show specific bands indicating antibodies to B. burgdorferi proteins.

• For IgM Western blots, at least 2 of 3 specific bands must be present,
• while IgG Western blots require 5 of 10 specific bands, as outlined in the current guidelines for laboratory diagnosis of Lyme disease in the United States 1. This two-step approach improves diagnostic accuracy by reducing false positives that can occur with single tests. It's essential to note that antibodies may not be detectable in early infection (less than 30 days), so patients with early symptoms and known tick exposure might need treatment before antibodies develop, highlighting the importance of clinical judgment in diagnosis 1. Additionally, once antibodies develop, they can persist for months or years, so the test cannot distinguish between active and past infections. The use of 2-tiered serologic analysis is meant to aid the diagnosis of individual patients in the clinical setting, not solely for surveillance purposes, and its results should be interpreted accordingly 1.

From the Research

Interpretation of 2-Tiered Lyme Disease Test

The 2-tiered Lyme disease test is a diagnostic approach used to support the diagnosis of Lyme disease. The test involves two steps:

• The first step is an enzyme-linked immunosorbent assay (ELISA) or indirect fluorescence antibody test to detect serum antibody levels against Borrelia burgdorferi, the causative agent of Lyme disease 2.
• The second step is a Western blot test to confirm the presence of specific antibodies against B. burgdorferi 2, 3.

Test Results

The results of the 2-tiered test can be interpreted as follows:

• A positive result on both the ELISA and Western blot tests indicates the presence of Lyme disease 2, 4.
• A negative result on the ELISA test rules out Lyme disease, while a negative result on the Western blot test after a positive ELISA result may indicate early infection or a false-positive result 2, 5.
• The sensitivity and specificity of the 2-tiered test vary depending on the stage of the disease and the population being tested 2, 6.

Key Considerations

Some key considerations when interpreting the results of a 2-tiered Lyme disease test include:

• The test is not 100% sensitive or specific, and false-positive or false-negative results can occur 2, 3.
• The test is more sensitive for late-stage Lyme disease than for early-stage disease 2, 4.
• The use of alternative testing protocols, such as a two-EIA algorithm, may provide similar or better sensitivity and specificity than the traditional 2-tiered test 5, 6.
• The interpretation of test results should be done in conjunction with clinical evaluation and medical history 2, 3.

Testing Strategies

Different testing strategies have been evaluated, including:

• Standard 2-tiered testing with ELISA and Western blot 2, 3.
• Modified 2-tiered testing with two different sequential EIAs without immunoblotting 5.
• Two-EIA algorithm with a whole-cell sonicate EIA followed by a VlsE C6 peptide EIA 6. Each strategy has its strengths and limitations, and the choice of testing approach may depend on the specific clinical scenario and population being tested 2, 3, 4, 5, 6.