The Ministry of Health issued the guidelines for antigen detection tests for the identification of COVID-19. The use of these tests will initially only be allowed to the Costa Rican Social Security Fund since they will be used for public health reasons to increase the capacity and response of laboratories at local levels, taking into account that antigen tests are faster. and less expensive than currently used PCRs.
The test will only be performed on people with symptoms according to the definition of a suspected case in the national guidelines for surveillance of the COVID-19 disease. To perform the nasopharyngeal swab test, the person must be between day 1 and 5 of the date of onset of symptoms.
This type of testing will allow a more expeditious approach in the investigation of outbreaks in remote places, in institutions, communities, educational centers, long-stay homes, centers for deprived of liberty and work establishments, provided that in these places it is detected during the investigation symptomatic people.
The antigen tests allowed in the country by the rector of health must have a sensitivity (ability to correctly identify an individual who has the disease) at least 80% and a specificity (ability to correctly identify an individual as free of the disease). disease) of 95%.
Due to its low sensitivity, it is necessary to perform a false negative control in order to identify possible cases that the test could not detect, so any negative case will require a confirmatory negative PCR test. To do this, the same negative sample that was processed for the antigen test will be sent to the CCSS laboratory network for confirmation. The patient will not be able to interrupt her quarantine or isolation until obtaining the confirmatory result.
Antigen tests detect the presence of viral proteins through an immunocapture format. Viral antigens can be detected when the virus is actively replicating, making this type of assay very specific.