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Guilherme Mazui

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What is the Difference Between Antigen and NAAT Test?

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The main difference between antigen and NAAT (nucleic acid amplification test) tests lies in their sensitivity, the type of viral material they detect, and the time it takes to get results. Both tests are used for the diagnosis of COVID-19, but they have different characteristics:

  • Antigen Tests:
  • Detect specific viral antigens in a specimen.
  • Provide results relatively quickly, usually within 15-30 minutes.
  • Less sensitive than NAAT tests.
  • A single negative antigen test result should not be used to rule out infection.
  • Repeating a negative antigen test at least 48 hours apart is recommended for better detection.
  • A follow-up NAAT/PCR test may be needed to confirm results from an antigen test.
  • NAAT Tests:
  • Detect genetic material (nucleic acids) from the virus, specifically RNA sequences.
  • More sensitive than antigen tests.
  • Considered the most reliable tests for detecting SARS-CoV-2.
  • Can be performed in a laboratory or as a point-of-care test, with the latter generally having lower sensitivity than laboratory-based tests.
  • Results for laboratory-based NAATs can range from less than an hour to more than a day, while point-of-care NAATs can provide results in about 15-30 minutes.

In summary, antigen tests are quicker but less sensitive than NAAT tests. Due to their lower sensitivity, antigen tests may require repetition, and a follow-up NAAT/PCR test may be necessary to confirm the results. On the other hand, NAAT tests are more sensitive and considered the most reliable tests for detecting SARS-CoV-2, but they may take longer to provide results.

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  • What is the Difference Between Antigen and NAAT Test?
  • Comparative Table: Antigen vs NAAT Test

    • Comparative Table: Antigen vs NAAT Test

    Here is a table comparing the differences between antigen and NAAT tests:

    Feature Antigen Tests NAAT Tests
    Definition Antigen tests detect the presence of specific antigens, which are protein molecules found on the surface of pathogens, indicating an active infection. Nucleic Acid Amplification Tests (NAATs) detect the nucleic acid sequence of the infectious agents, indicating the presence of the pathogen.
    Sensitivity Antigen tests are less sensitive than NAATs. They can return false negatives, especially when testing before symptom onset when the level of antigens in a specimen is lower. NAATs have a higher sensitivity, making them more likely to detect the presence of the pathogen.
    Specificity The specificity of antigen tests is comparable to NAATs, meaning that false positive test results are unlikely when an antigen test is used according to the guidelines. NAATs are considered more accurate than antigen tests.
    Cost Antigen tests are generally lower in cost compared to NAATs. NAATs are often more costly to perform than antigen tests and may require specialized laboratory equipment.
    Testing Time Antigen tests offer faster results compared to NAATs. NAATs typically take longer to produce results due to the need for laboratory equipment and analysis.
    Confirmation Negative antigen test results should be confirmed with a NAAT or repeated with additional testing. NAATs are considered the gold standard for diagnosing infectious diseases.

    Please note that these differences are general and may vary depending on the specific test and pathogen being tested for.

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    Guilherme Mazui

    Guilherme Mazui is graduated in journalism from the Federal University of Minas Gerais (UFMG) and a master's degree in Communication from the University of São Paulo (USP). In addition, he has experience in advertising writing and has worked as a content editor in several companies.