His is how the coronavirus testing looks like
Relaxation of the lockdown measures keeps advancing in Spain, and with it the return to working places. Beside the protection and hygiene measures set by authorities (hand washing, social distancing and usage of masks), undergoing massive testing for the detection of Covid-19 is one of the main tools to fight the virus, as it allows to sort out who’s contaminated and isolate those individuals to avoid further spread of the pathogen.
There are a series of different tests that can be taken and not all have the same reliability standard. Interested in knowing the differences? We can tell you.
Three are the main tests to determine if someone is or has been infected by Covid-19: the PCR, that detects and quantifies the virus, and is considered the most reliable; the serological tests, both of antigens and antibodies; and the immunological tests, also know as fast test. The serological and immunological tests show the immunological response to the pathogen, in different phases of its development, and therefore depending on which phase the patient is one of them is the most recommended. The reliability of those tests keeps being questioned all around the world due to the high incidence of false positives.
The PCR (polymerise chain reaction) is a test that allows the identification a fragment of the genetic material of a pathogen, or in other words, the presence of the virus at the body. It is recognized as the most efficient of the tests (90%+ accuracy) and therefore is the one recommended by the World Health Organization for the detection of the virus, nevertheless it poses a series of difficulties, as it can only be processed at a lab and its result takes 3 to 6 hours to be available. The PCR is fundamental to establish a basic distinction between the affect patient that still has the virus and the one that don’t, even in the case of asymptomatic individuals.
The high cost of this test as well as the long processing time to get its results has been the main driver for the implementation of the so-called fast tests, faster and simpler (it only takes 15 minutes to get the results and no healthcare staff is required), while they’re less reliable, what has led the WHO to discourage its usage. Another relevant difference between those and the PCR is that they do not identify the RNA of the virus, that is they either identify the antibodies produced using the blood sample or the proteins that are present at the respiratory tracts that is obtained through a nasopharyngeal exudate. Is summary, they show the immune response of an individual.
There are to types of fast tests. On one side there are the antigenic tests that make use of material obtained from the nose of the mouth, obtained with a swab, and that serve to detect the proteins (antigens) produced by the immunological system to attack viruses and bacteria. This test is recommended when one is at an initial phase of a disease. Main advantage is that it can be performed at one’s home, without the presence of a specialist and the results are available in 15 minutes.
Another test is the serological or antibody test, where a blood sample is taken to identify antibodies that compose the defenses of the individuals days after it is infected by the virus. The major inconvenience is that it cannot identify the virus during the first seven days of an infection and neither on the case of asymptomatic patients. These tests detect antibodies (IgM, the first one to fight an infection and also and IgM, the most abundant and present at a later stage of the process).
In any case, the response to this virus, as stated by the WHO from very early days of the pandemic is “test, test, test”.Back to News