For rapid antibody tests and ELISA tests the interpretation is the same.

The ELISA test is considered more reliable and also gives a quantitative figure of the amount of antibody (as opposed to a simple positive/negative result with the Rapid test).

There are 4 possible results:

  1. IgM negative, IgG negative.
    1. There is no evidence of current infection or previous infection.
    2. Remember that it takes a minimum of 4 days from the start of symptoms, or 7 days from exposure to the virus before the antibodies show up positive. This means that the antibody test cannot detect an infection in the initial stages.
    3. If there is a suspicion of recent infection in spite of this result a PCR test can be done, or repeat the antibody test after a few days.
  1. IgM positive, IgG negative:
    1. This suggests infection in the early stages of the disease.
    2. If the result does not coincide with the clinical picture (for example, if there are no symptoms) it could be a false positive. The result can be confirmed with a PCR test or, if the test was a Rapid antibody test, by doing an ELISA test, which is more reliable and uses a different method.
  1. IgM positive, IgG positive:
    1. This suggests infection in the intermediate stage of the disease.
    2. Infectivity is likely to be low.
  1. IgM negative, IgG positive
    1. There is recovery from the disease and the patient is not infectious
    2. There may be some immunity to Covid-19, although it is not known yet to what extent and how long that immunity may last. Precautions should still be taken.

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Post by: Atlantic Clinic on 21 Aug 2020