How does nucleic acid amplification test work

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CDC is not responsible for Section compliance accessibility on other federal or private website. Cancel Continue. Once collected, samples are placed in an extraction buffer or reagent and tested for the presence of SARS-CoVspecific antigens. They detect the presence of virus-specific proteins, called antigens, from patient specimens. As of Aug. Results are produced quickly, generally within 15 minutes, and can be performed near the place and time of patient care as opposed to a separate laboratory setting.

If the viral antigen is detected, it indicates that the virus is present. Diagram of a rapid antigen test. Sample is applied to the test strip and if antigen is present, it is bound by antibodies linked to detector molecules, as well as antibodies immobilized in the test line further down the strip. While at-home tests may be the quickest and most convenient option, they may not be the most appropriate for all situations. If you want to be sure the test you are buying is authorized by the FDA, visit our tables of molecular , antigen , and serology and adaptive immune response in vitro diagnostic emergency use authorizations EUA for more information.

Using the search box in the EUA tables you can use keywords to search and filter the type of test or collection kit you are looking for. Using this search, as new tests are authorized for use, consumers can access up-to-date information on authorized tests and collection kits.

Different tests are authorized to be used with different types of samples. The most common sample types are:. Swab samples use a swab similar to a long Q-Tip to collect a sample from the nose or throat. The types of samples include:. Saliva samples are collected by spitting into a tube rather than using a nose or throat swab. Some antibody tests use blood from a finger stick. This saves time and test materials when only a very small number of positives are expected, allowing labs to test more samples.

If the test is positive, showing the presence of the virus that causes COVID, everyone is retested separately, either by taking a new sample or testing a remaining portion of the original sample, to find the samples that are positive. CLIA certification is a requirement for clinical laboratories providing diagnostic testing. An antibody is protein that is a normal part of the immune response to many types of infections. Our bodies develop antibodies in the days and weeks after being infected.

Antibodies are specific for different infections — as part of the immune response, the antibody attaches to specific parts of the germ. For example, there are antibodies for influenza and different antibodies for hepatitis C. This protein is only found on the virus and is not a component of the current SARS-CoV-2 vaccines, so a positive result indicates you have been exposed to the virus and have developed antibodies against it.

It does not provide information on how much antibody there may be. This protein is found within vaccines or produced as a result a result of vaccination, in addition to being a part of the SARS-CoV-2 virus.

A positive result for this test can indicate either a past infection or it may indicate vaccination against the virus. The spike antibody tests is a "semi-quantitative" tests which provides a numerical result that indicates the relative amount of antibody present in the sample.

However, positivity likely declines over time, so distant past infections may not be detected by the assay. Information provided by the assay manfucturer Abbott indicates that This means the test will be positive when the person never was infected. This is true for all antibody tests, including tests that perform well like those used at UW Medicine. In some cases, immunocompromised patients may have a negative test result despite prior COVID infection due to lack of or delay in development of detectable antibodies.

The antibody tests are not used to diagnose acute infections.