With the Christmas vacations approaching, the sale of antigen checks has exploded, as many human beings stockpile in an effort to thoroughly reunite with their own circle of relatives and friends. For this reason, below we try to answer some questions that may arise about this method of diagnosing covid.
When Is The Best Time To Get An Antigen Test?
The advice is to do it inside seven days after contamination or inside 5 days after signs appear. If we do it the same day or the day after having been in contact with a person who has tested positive that same day, the result will not be reliable.
If The Result Is Negative, Can I Be Sure That I Am Not Infected?
Absolutely. In these rapid tests, the only really reliable result is a positive, since they can produce false negatives. Its usefulness is above all to detect asymptomatic people who are infected. If it is suspected that you may be infected and the test result is negative, it is always better to corroborate it with a PCR and continue to maintain all safety measures.
How Effective Are They?
When we go to buy it, we must make sure that the sensitivity is greater than 90% and its specificity greater than 97%. If more false negatives are produced than in a PCR, it is because either the instructions are not followed correctly and the sample is not taken well, or because of the type of reagent or the low sensitivity of the test, due to the time of the evolution of the infection in which the test is done or because the viral load is very low.
What Types Of Tests Are There?
There are two. The nasal and the buccal. In the first, the sample is extracted by introducing the swab into the nose, about 2 or 3 centimeters. The buccal is more complicated since it is necessary to obtain a sample of saliva. Here you have to extract from the throat, not the mouth. You have to cough two or three times and then extract the sample. In both cases, the waiting time for the result is the same, between 15 and 20 minutes.
Can I Go To The Pharmacy And Have It Done There?
Yes, not all but many pharmacies carry out these tests and communicate the results to Health, so it will be reflected in our profile of the Health app.
What Is Its Price?
Its price is free, with which each manufacturer - currently about 20 are marketed in Spain - and each pharmacy can set the price they want. In any case, the average price is around five euros and all enjoy a reduced VAT rate of 10%. Keep in mind that pharmacists will charge us for providing this service –around 10 euros–, in addition to the price of the test. In the case of children, they can take the test in pharmacies for free. In a laboratory, the price for taking an antigen test is just over 30 euros.
Are They Used To Traveling?
Yes, but in this case, it is not worth doing it ourselves. You have to go to a pharmacy or an approved laboratory so that the result is officially recorded in our covid passport or so that they issue us a certificate with the negative result.
Are Currently Sold Antigen Tests Still Reliable For Detecting An Omicron Infection?
Yes, nothing changes and they remain just as reliable or unreliable depending on whether the result is positive or negative. Yes, there may be a slight loss of sensitivity, but performance will continue to be optimal, because what the tests detect is the protein S (spike) and N (nucleoprotein) of SARS-CoV-2, and in the variants what changes are alterations in S, but protein N remains stable, so tests are still useful to detect it.
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