Usability and Effectiveness of At-Home COVID Testing Kits
At-home COVID-19 testing kits give rapid results and can be taken anywhere. They are nasal or salivary; that is, they use saliva as a biological liquid with which to detect the presence of any antigens. If a person tests positive, certainly that is a person who has been infected. The problem is when they are negative because we are not sure that the negativity corresponds to the reality of the facts. So the use of rapid tests, on the one hand, is helpful if it intercepts the positives, but if it does not intercept the positives because the sensitivity is not so high, then it can cause damage because of a false result.
At-home COVID testing kits can be useful for identifying asymptomatic people but only for those who have a good viral load. Often asymptomatic people have a low viral load, so in this case, we risk not intercepting them, giving false negativity and therefore false security. I believe that these swabs, which are certainly not as reliable as a molecular test, should be used in those situations where it is necessary to have a differentiated path for those that are positive and those that are negative. I believe that these swabs can be very useful, for example, in the peripheral emergency room, where people who have symptoms arrive and that symptomatology may be due to COVID or another pathogen. The swab, in that case, will respond adequately, and then the credibility of the positivity or sensitivity will be very high.
In other contexts, however, such as supermarkets or cinemas where one is asymptomatic, then the lack of symptoms in the presence of an infection could be determined by a low viral load that the quick swab is not able to intercept. This can be a problem because it could, on the contrary, give false certainties. In these contexts, I would recommend using the personal protective equipment that we have learned to use and which are now widely available, such as masks or gloves, for example, which in some way, by keeping the distance, determine a certain safety with respect to any interpersonal contact.
After performing a DIY swab, if the two lines C and T appear on the device, it means that you test positive for the SARS-CoV-2 coronavirus. Without panicking, you should contact your doctor or the health authority of your region to get all the information on the steps to follow. As indicated, do-it-yourself swabs are not officially recognized; therefore, they contact person may ask you to make a molecular swab or an “official” antigenic (for example, at a hub drive-in) to confirm positivity. Of course, it is always a duty to isolate yourself from others and, in the event that you have to live with other people, it is important that everyone wear a mask. The cohabitants, being close contacts, in turn, must follow the quarantine. We reiterate the concept that DIY swabs are not used in pandemic management, and Ministry of Health guidelines and expert recommendations should always be followed.
In just over a year, we have gone from not having enough masks to cover our nose and mouth to be able to make a swab directly at home for the self-diagnosis of positivity to the COVID-19 through the at-home COVID testing kits. There is no shortage of criticalities regarding this kind of test – indeed, as we will see, there are several – but in general, it can be a further small step forward towards an increasingly accurate mapping of the real circulation of the virus. Conceptually, it’s all pretty simple. The at-home COVID testing kit will be on sale in a large number of shops, not only pharmacies but also supermarkets, shops and in general in any business that decides to distribute them. Potentially, we could also find them at the bar or restaurant, in hardware stores, in stationeries and at newsstands: since it is not a drug, in fact, the sale has much less stringent rules. A bit on the model of the masks, which can now be purchased everywhere, paying attention only to the fact that they are certified models.
Once you have purchased the at-home COVID testing kit and brought it home (since to use it, you need to remove the mask, it is better to use it quietly and in a suitable place), you will need to insert the special sterilized stick in the nasal cavity, take the biological material, deposit it in a special well sample and then use the extraction solution – the reagent provided in the kit itself – with your dropper to find out the result. It is roughly necessary to wait a quarter of an hour between the execution of the test and the availability of the result, which is qualitative and visually similar to a pregnancy test. According to some manufacturers, 10 minutes of waiting are enough, and in almost all cases, after 20 minutes, the result may no longer be legible: for this reason, it is advisable to bring a watch and pay attention to how much time elapses.
The test result is positive if the specific proteins (antigens) that identify the Sars-Cov-2 virus are identified and is negative if they are not detected. In general, it is also possible that the test result is null, in the sense that if the line corresponding to the quality indicator is not observed, it means that something did not work, and therefore the test is certainly not valid.
Both from an intrinsic and scientific point of view, the do-it-yourself kit for the antigen test has some objective limitations that it is good to know. First of all, unlike molecular tests that are based on the amplification of viral genes through real time PCR, antigenic tests do not look for the genetic material of the virus but rather specific proteins. Even if there is still a one-to-one correspondence between the virus and what you are looking for, in general, an antigen test has a lower sensitivity and specificity, i.e. a higher probability of obtaining false negatives (especially if the viral load in the body is low) and false positives. When the viral infection is in the acute phase, it can even reach 97% -98% reliability, but in the early stages of Covid-19, it also drops to 80%. Added to this is that, in general, a nasal swab is less reliable than an oral, rhino-pharyngeal sample, but for practicality today, in many cases, the nasal swab is preferred even when a molecular test is performed.
Given the informal, artisanal nature and full autonomy and freedom of performing the do-it-yourself test, it is not yet clear how the outcome interfaces with the rest of the national system for recording cases and contacts, including isolations, quarantines and everything in between. Simply put, if the test can be freely purchased without any registration, public health will have no way of identifying who took the test. Probably, therefore, the do-it-yourself test will not be able to be used to sanction the end of quarantine or a cure from Covid-19, and in the same way, a possible positive result will have to be confirmed by other independent tests. However, given that the bureaucratic evolution is very rapid, it is not excluded that there may be news or changes of direction in the coming weeks.
The antigenic tests, both professional and do-it-yourself, can have good sensitivity and can help contain the infection thanks to some characteristics that the molecular swab does not have: very wide accessibility, low cost, very fast result, possibility to repeat the test more times, to find cases promptly. In addition, do-it-yourself has ease of use and a less “invasive” sampling than that required by the molecular swab or by professional tests, which is particularly useful in the case of small children and schoolchildren in general.
Some experts, however, said they were opposed to the use of antigen tests, even professional ones (i.e. those used by pharmacists or other health professionals) because, according to them, they are much less sensitive than the molecular swab and therefore too little capable of containing the infection. The criticism is even harsher towards self-tests because (according to the detractors) the hand of the professional would be more skilled than that of the citizen in making the sample correctly, a fundamental step for having a reliable result.
