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Why positive controls are important for Covid-19 rapid tests

As part of good laboratory practice (GLP), it is important to use quality controls that ensure that the test functions correctly, regardless of the samples tested. This is the only way to ensure that negative or positive result are not caused by incorrect handling or a damaged test.


Positive and negative controls are suitable for this purpose. These controls are performed with the antigen rapid test and should lead to a positive or negative result in every case. If the expected result is not obtained, this means that the regular ones are not reliable either.


The use of positive controls is particularly important for professional operation in test centers and hospitals. For this reason, this is also increasingly required by associations of panel doctors and supervisory authorities.


What is a positive control ?

The positive control is a swab that is coated with an artificially produced viral protein. This protein, nucleocapsid porotein, is the component of SARS-CoV-2 that is detected by the Testsealabs Antigen Rapid Test. The test stick does not contain any virus or infectious material and there is no health hazard.


How to use a positive control?

The positive control swab must not be used to perform a swab. This is not necessary as it already contains a simulated sample. Instead, the positive control is handled as a regular specimen and dissolved in the specimen buffer according to the package insert and then applied to the test cassette. The result is then interpreted according to the package insert after 10 to 15 minutes. For optimal quality assurance, the positive control should be handled exactly like a regular specimen, including all waiting times and any deviations from the package insert. In the best case, this is done in a blinded manner together with regular samples.


What can lead to a false test result?


  • Incorrect storage conditions - Some components of rapid antigen tests are very sensitive to extreme temperatures. Storage in an environment that is too warm or too cold can then lead to damage of the test.


  • Incorrect handling - Both the performance and the interpretation of antigen rapid tests are described precisely in the package insert and are a prerequisite for a correct result. Especially when performing many tests, there is a risk of errors creeping into the process and falsifying the result.


  • Incorrect test environment - Antigen rapid tests contain a sensitive membrane in which the sample comes into contact with the anitbodies. This reaction can be compromised by temperature extremes, humidity levels that are too high or too low, drafts, or contaminants in the air.


  • Damaged batches - The production of medical devices is subject to strict quality controls and, in the case of Testsealabs, has been audited by TÜV-Süd. However, individual batches may not be of the desired quality and results may be compromised. In this case, a quality assurance system can detect damaged batches at an early stage.



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