Here’s how the rapid COVID tests that will reach pharmacies without a prescription work: Features and effectiveness


Posted: Wednesday July 14 2021 8:32 AM

The Ministry of Health will approve a royal decree authorizing the general sale and without a prescription in pharmacies of antigen tests for self-diagnosis. That is, the fastest and easiest tool to detect COVID, can now be purchased without any kind of prescription. Like a pregnancy test, like those that measure glucose.

Now, what exactly does this test consist of, is it effective? The first thing to keep in mind is that, as the Spanish Agency for Medicines and Health Products (AEMPS) explains, it is essential when the test is used.

Specifically, anyone who wants to check whether or not they have coronavirus should be tested within the first five days of suspected infection. Basically the time when the viral load is highest and therefore the virus is most detectable. We review the main features of this detection instrument:

How effective are rapid tests?

AEMPS clearly recommends these tests. As the entity writes, in order for a test to be purchased at a pharmacy, it must meet “minimum performance requirements”. This is where the concept of “specificity” comes in – which dictates whether a test is reliable or not.

The tests validated by the Medicines Agency must have a specificity of at least 97%. In other words, out of 100 tests performed by 100 healthy subjects, at least 97 of them should be negative.

However, AEMPS also requires a minimum percentage regarding the “sensitivity” of the test – unlike specificity, this parameter measures the probability of correctly diagnosing a sick individual, such that it does not result in a false negative – . In this case, the minimum value must be greater than or equal to 90%.

At the same time, to have the approval of official entities, the test must contain the CE mark, followed by four digits of the notified body that evaluated it. To verify this, you can visit this web page where the European Union collects the tests that have passed the filter.

How is the test used?

As with all types of tests, the manufacturer’s instructions should be strictly followed. Otherwise, the result could be affected. Typically, these tests are equipped with three components: the detector device, a tube of liquid, which contains the reagent, and a lancet or swab that must be inserted into the nose (in the two holes).

Then this swab should be introduced into the liquid for about 15 seconds, and of this remaining liquid, three drops should be added with a pipette into the detection device. Then you need to wait about 10 minutes until the result appears.

How do I know if I am positive or negative?

As you will see in the detection device, the test has two fonts (C and T), which refer to “control” and “test”. For the result to be positive, the two lines corresponding to each letter must be visibly marked.

On the contrary, if you have a negative test, you will only see the line corresponding to the letter C. Remember, this line must be completely visible, because otherwise the test could have been defective or an error could have been made. been made in its use. Therefore, it would be invalid.

And what to do after knowing the result?

If you have tested positive, it does not matter whether you have symptoms or not: you must undergo an immediate quarantine, as well as contact the health services of your autonomous community so that they know your condition and can do a PCR test.

On the other hand, if your test is negative, it does not mean that you do not have the disease. As we said, the effectiveness of these tests is by no means foolproof, so you could have the disease and simply show a low viral load or have taken the test at the wrong time (it must be remembered that it must be done within the first week of possible contagion). In the latter case, health authorities also recommend isolating yourself and, again, contacting medical services.

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