How to avoid mistakes with at-home COVID-19 tests
Kits with the rapid antigen (or "lateral flow") tests, designed to detect the presence of a specific viral antigen, come with a detailed instruction leaflet, but some people nevertheless make mistakes that can distort the results.
The kits should be kept in a place that's neither too cold nor too warm, so neither in a refrigerator nor in direct sunlight. Studies show that improper storage can cause incorrect test results.
"They can be stored at normal room temperature," Junge-Hülsing said. The proper temperature range is normally given on the packaging or in the instruction leaflet.
It's important that the kits always be at room temperature when used. So if they were stored in a cooler place, they should be given time to reach room temperature before use.
Proper hygiene is essential for correct test results. The test area should be clean, and you should wash your hands thoroughly before taking the test.
If you're testing several people, for example, yourself and your children, you won't be able to handle all the extraction tubes at the same time. So if the kits don't contain an extraction tube holder, Junge-Hülsing suggests clipping clothes pegs to the bottom of the tubes, enabling them to stand upright without falling over.
A COVID-19 self-test normally requires taking a swab sample from both nostrils. You might think that swabbing one nostril is sufficient, but it isn't, "because one swab might collect too little nasal discharge," Junge-Hülsing explains.
A sign that the swab may have collected relatively little nasal discharge, Junge-Hülsing says, is the color of the line in the control region of the test strip.
"A color that's very faint indicates little discharge," he noted. This increases the risk of a false negative result.
According to immunologist Dr. Martina Prelog, a member of the German Society for Immunology (DGfI), there are other possible reasons for a faint control line: for example, the test kit was stored improperly or too little liquid solution was provided.
Swabbing should be done carefully and gently. The self-tests don't require inserting the swab all the way to the junction between your nose and throat – 2 to 4 centimeters into the nostrils is sufficient.
Reading the result
According to Junge-Hülsing, most errors occur when it comes to interpreting the test result. Many people think a colored line in the region of the test strip marked "C" means the result of the test was positive. "C" stands for "control" though, and not "COVID-19" or "coronavirus."
"T" stands for "test," and this is the region of the test strip that shows whether the result is positive or negative. So if there are colored lines in both the control line region (C) and test line region (T), the test is positive. If a colored line appears only in the control region, the result is negative.
If a colored line appears only in the test line region or no lines appear at all, the test is void.