From the Guidelines
The Vector test is not a recommended diagnostic tool for Lyme disease, and instead, a 2-tiered serologic analysis consisting of an enzyme-linked immunoassay or immunofluorescence assay, followed by reflexive immunoblotting, is the preferred method in the United States. When considering diagnostic tests for Lyme disease, it's crucial to understand the different stages of the disease and the appropriate timing for testing. According to the study published in Emerging Infectious Diseases 1, the sensitivity of the 2-tiered testing is low (30%–40%) during early infection, but it increases to 70%–100% for disseminated Lyme disease, with a high specificity (>95%) during all stages of the disease. Some key points to consider when diagnosing Lyme disease include:
- The presence of erythema migrans (EM), which is a classic sign of localized infection, and can be diagnosed without laboratory testing in patients from Lyme-endemic areas 1
- The use of laboratory testing to confirm the diagnosis in patients without EM, with the 2-tiered serologic analysis being the recommended method in the United States 1
- The importance of proper interpretation of test results, taking into account the symptoms and timing of illness 1
- The limited use of other diagnostic tests for Lyme disease, such as the Vector test, which is not mentioned as a recommended diagnostic tool in the study 1.
From the Research
Vector Test Overview
- The vector test, also known as the dengue NS1 antigen rapid test, is a diagnostic tool used to detect dengue virus infection in acute phase patients 2, 3, 4.
- The test has been shown to have good sensitivity and specificity, with some studies reporting sensitivity rates of up to 99.2% and specificity rates of up to 96.0% 4.
- The test is particularly useful in difficult to reach areas, where access to laboratory facilities and trained personnel may be limited 4.
Comparison with Other Diagnostic Tests
- The vector test has been compared to other diagnostic tests, including ELISA, real-time RT-PCR, and virus isolation 2, 3, 5, 6.
- Studies have shown that the vector test has similar or better sensitivity and specificity rates compared to these other tests, particularly in the early stages of the disease 3, 6.
- However, some studies have also reported variability in the performance of different commercial diagnostic tests, highlighting the need for careful selection and evaluation of tests for use in clinical practice 5.
Factors Influencing Test Results
- Several factors have been identified as influencing the results of the vector test, including the duration of illness, the presence of IgG antibodies, and the timing of sample collection 2, 6.
- Studies have shown that the sensitivity of the test is higher in the early stages of the disease, and that the presence of IgG antibodies can reduce the sensitivity of the test 2, 6.
- The timing of sample collection has also been shown to be important, with samples collected after the fifth day of illness having lower sensitivity rates 6.