Teste de doença de Lyme pode ser falso negativo?

Diagnosis of the Lyme test is essential to initiate treatment as delayed treatment can increase the severity of the disease, treatment becomes more complex and the body also suffers. The diagnosis of the disease is initially made by physical parameters such as travel history and symptoms. After that, the blood test is done to get clear results. The blood test is done in two phases. In the first phase, the enzyme-linked immunosorbent assay (ELISA) is performed as a screening test and subsequently confirmed by the Western blot. Sometimes a blood test, which depends on antibody identification, can give false negative results.

It should be borne in mind that the diagnostic test detects the antibodies present in the blood. These tests do not identify the presence of bacteria in the body. In addition, the test result also depends on the duration of the infection. Since these tests do not indicate the presence of bacteria, these are known as indirect tests. Indirect tests, for certain reasons, may give a false negative result. False negative result means the person is infected while the test is negative. This may be due to the following reasons:

  1. Infection length:  As the test identifies the presence of antibodies in the blood, if there are no antibodies, the test will be negative. However, producing a measurable amount of antibody requires 4-6 weeks after infection. Therefore, if the test is recommended only based on  migratory erythema  prior to this period, the test will not detect antibodies and give false negative results.
  2. Immune System Suppression:  If the patient’s immune system is suppressed due to other underlying conditions, the body will not be able to produce antibodies and thus will not be detected in the test. This will provide a false negative result.
  3. Different Strains:  If any other strain causing Lyme disease has invaded the body, the test will not identify the antibody present in the blood and thus give a false negative result.
  4. Seronegative  patients : These patients do not produce antibodies.

To reduce the false negative results of the indirect method, certain doctors advise the direct methods in which bacteria are identified. Such tests may include polymerase chain reaction, culture testing and antigen detection. These tests do not depend on the body’s response against bacteria.

Lyme Disease Diagnosis

Common symptoms of Lyme disease are fever, headache, joint pain and rash. These are not specific features of Lyme disease and may occur in case of other diseases. Thus, the diagnosis of the disease is made mainly based on physical parameters and later confirmed with blood tests. Following are the physical parameters that help determine the possibility of Lyme disease:

  1. History:  Lyme disease occurs mostly in some areas, such as the northeast and the upper midwest. Thus, if one has traveled to areas where the occurrence of Lyme disease is high, one may have contracted Lyme disease.
  2. Signs and Symptoms:  Signs and symptoms also help in the diagnosis of Lyme disease. Circular eruption, also known as migratory erythema, may be a typical feature of Lyme disease, which increases the chances of Lyme disease.
  3. Blood Test:  The blood test is done to detect antibodies that are developed against bacteria. Testing is a two-step process, where the first is the screening test and the second is the confirmatory test, and consists of the following steps:
    • Enzyme Linked Immunosorbent assay (ELISA) and,
    • Western blot test.

Conclusion

Tests that identify the presence of antibodies in the blood may give false negative results in Lyme disease. Reasons may include incorrect test time, immunosuppression, different strains or the patient being seronegative. This disadvantage is not present in the direct test that identifies the presence of bacteria.

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Especialista em Dor at | 425-968-1599 | [email protected]

Eu sou o Dr. Ruby Crowder e sou especialista em medicina pulmonar e cuidados intensivos. Eu me formei na Universidade da Califórnia, em San Francisco. Eu trabalho no Hospital Geral de São Francisco e Centro de Trauma de Zuckerberg. Eu também sou professor associado de medicina na Universidade da Califórnia, em San Francisco.

Eu pesquisei a epidemiologia e o manejo da tuberculose em países de alta incidência e publiquei muitos remédios e artigos relacionados à saúde sobre o Exenin e em outras revistas médicas.

Finalmente, gosto de viajar, mergulhar e andar de mochila.

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