Taking a rapid antigen test at home helps to reduce the spread of Covid-19.

However, it’s crucial that they’re handled properly to get an accurate result.

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.

Ear, nose and throat (ENT) physician Dr Bernhard Junge-Hülsing points out typical errors and how to avoid them:

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,” Dr Junge-Hülsing says.

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 persons, e.g. 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, Dr Junge-Hülsing suggests clipping clothes pegs to the bottom of the tubes, enabling them 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”, Dr Junge-Hülsing explains.

A sign that the swab may have collected relatively little nasal discharge, he says, is the colour of the line in the control region (C) of the test strip.

“A colour that’s very faint indicates little discharge,” he notes.

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.

These could include improper storage of the test kit or too little liquid solution.

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 - two to four centimetres into the nostrils is sufficient.

According to Dr Junge-Hülsing, the most errors occur when it comes to interpreting the test result.

Many people think a coloured 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 coloured lines in both the control line region (C) and test line region (T), the test is positive.

If a coloured line appears only in the control region, the result is negative.

If a coloured line appears only in the test line region or no lines appear at all, the test is void.

 - dpa