Coronavirus tests: How helpful are antigen COVID tests? Do they give accurate results?

Over the course of a year, we have seen a lot of advancements and betterments in the field of COVID testing and diagnosis. While the cases continue to rise, we now have a lot of antigen and quick-result prompting COVID tests, which can tell if you are at risk. They are also proving to be helpful when people have started to resume pre-pandemic activities and need clarity with their health. With signs of a third wave approaching soon, experts also suggest that there may be a higher demand for quick, at-home testing kits to get people the answer whether or not their symptoms are actually COVID-19 related.

But, with all their benefits, how accurate are they? Are they something to be stocking up on, before the third wave arises?

Most self-COVID tests authorized for use in India and abroad are a form of antigen testing, which tell you about your COVID status (whether positive or negative) in a short time.

Antigen and molecular tests used for COVID testing work to identify the presence of viral components in the body. Antigen tests, particularly, which form the backing of several quick-result delivering at-home COVID tests use a technology to trace the protein in the virus strain in the body and dole out a positive or negative test. Compared to this, molecular testing, also known as PCR (Polymerase Chain Reaction ) testing helps identify the RNA, or the genetic component of the virus, and is hence ranked to be gold-standard tests.

Both the tests, however, are administered in the same manner- using a throat/nasal swab that sample the saliva to trace the virus. The reason why PCR and antigen tests have such a varied difference in respect to the result delivery times is that while PCR technology requires specialized, often expensive diagnostic equipment and runs the virus component through repeat cycles to find the result, antigen tests look for the protein, and the results can be easily verified at an economical, time-effective manner. So to say, while self-COVID tests can deliver results in 15-20 minutes, PCR tests can take upto a minimum of 24 hours to deliver results, or more if there's a high demand for the testing.

Now, while antigen tests have been considered to be a great alternative to RT-PCR testing ever since they were first authorized for use, the demand for at-home COVID antigen tests have risen sharply in the current timeline- when breakthrough cases are rising, more people getting out and the Delta variant quickly spreading- meaning that there's a greater need to know about one's health and COVID status early on.

Antigen tests are also quite helpful since they deliver COVID results in a much shorter timeline than the average PCR tests. Especially with the surge caused by the Delta variant, which spreads and affects people quickly, antigen tests can alert a person about their symptoms and help them take a quick call. Right now, with the deluge of infections caused by respiratory infections like dengue, malaria, flu or even a simple viral fever, getting a quick analysis can help people seek clarification and get neccessary treatment.

Having explained the benefits, it's important to remember that with any test, there can be chances of getting false positives and negatives. With antigen tests, the likelihood of getting false negatives can be slightly higher, and make it less effective or trustable than gold-standard PCR tests.

As convenient and helpful as the tests are, antigen tests aren't 100% accurate and getting a negative on the test should not be considered fully true. One primary reason as to why this happens is that the test also sequences the protein part, and not the entire virus RNA, which can increase the chances for false results to come up. False negatives may not happen every time when you take the tests, but they can nonetheless occur.

COVID test kits also work on parameters like specificity and sensitivity. While some tests are better capable than others, antigen tests are less 'sensitive' than molecular PCR tests, but do help diagnose an infection. Therefore, if you do have symptoms but get a negative result (and suspect high exposure to a COVID+ person), take a backup, preferably a PCR test done.

The demand for COVID testing has risen unproportionally during the second wave and following months when the Delta variant became a dominant threat. Even while we do talk about these tests being a little less sensitive than molecular ones, they may still be somehow reliable and correctly pick up the infection if your symptoms or someone around you suspects COVID-related symptoms. With the Delta variant known to cause symptoms quite early and be extremely transmissible, having these tests handy can be quite useful.

However, it should be remembered that to exactly sequence the Delta variant, genomic testing is required- which can only be conducted via proper diagnostic laboratories.

Nonetheless, if you do plan to use these tests or keep antigen tests at home, do keep in mind that while there can be some chances of false positives and negatives, the tests are reliable, as long as you administer them right. Do read the instructions or the manual properly, and follow all steps to minimize the chances of getting wrong results.

Much like other tests, antigen tests can also lead to wrong or less accurate results if taken at the wrong time- tests administered too early, or too late, can deliver wrong results. If you do spot a negative, even with the severity of symptoms that state otherwise, do remember to get another test done.