The Food and Drug Administration (FDA), the U.S. regulator, has issued an emergency authorization to proceed with the marketing of the first Covid-19 self-test for home use, providing results within 30 minutes. The kit, issued by Lucira Health Company, is a single-use molecular test available by prescription. The rapid test uses molecular amplification technology to detect the virus in infected people. The laboratory that has manufactured it ensures that its sensitivity is above 90%.
The test looks for traces of the genetic material of the coronavirus. Previously, diagnostic tests for Covid-19 had been approved for at-home use, but until now samples had to be sent to specialist laboratories - and the results took time.
This new method for coronavirus detection, which uses nasal swab samples, can be used by people who are over 14 years old, and in the case of under-age users, provided that they are done by a health specialist. It has also been authorized for all-age use in settings such as doctors' offices, hospitals, emergency care, and emergency centres, but in these places, the samples have to be collected by qualified personnel. In a statement, the FDA said that "the new testing option represents an important diagnostic breakthrough in fighting against the pandemic".
The kit includes a sterile swab, a sample vial, a test unit, batteries, and a plastic bag. The sample collected in the nasal swab is inserted into the vial, which then fits in the test unit and is analyzed. The results are displayed by a colour change on the LED indicators. Instructions on how to use the test are included in the package.
Three types of methods
Ten months after the outbreak of the pandemic, there are now three types of tests: PCR, antibody, and antigen tests. The former (PCR tests) have been most common and accurate during the early times of the health emergency. They work with the genetic code of the virus, and are operated by swabbing a sample from a potential patient in the throat or nose. The sample is amplified in a machine the size of a toaster, through which the specific genetic material of the coronavirus can be detected. This purified genetic material is then mixed with reagents, including some derivatives of the coronavirus itself.
Antibody tests, also known as serological tests, do not detect the virus itself, but detect whether the person has antibodies in his or her immune system to fight the coronavirus. The person who develops them has either already had, or is currently infected by, the virus. The tests are performed with a blood sample. Antibody tests are not usually used for diagnosis, but rather to have an idea of the expansion of the virus in a population group.
Antigen tests, which have been recently introduced, are a quick and easy way to find out the necessary results. Antigen is a term that designates any foreign substance, such as a virus or a bacteria. For example, antigenic tests for the flu or a strep throat can be performed in a doctor's office without expensive equipment, and the results can be seen within minutes. These work like home pregnancy tests, but in the specific case of antigens they look for a unique slice of the coronavirus, for instance, a specific protein. If it is present in sufficient quantity, the test will show a positive result. The immediacy of the result is of great relevancy.