I'd like to share with you an article from Dr Elize de Bruyn, Scientific Director at IMed Laboratories. As both Antigen and in laboratory PCR testing contribute to the daily number announced by Government, it merits understanding the different tests. To highlight one section:
"In laboratory PCR tests are the best diagnostic method, particularly in the early phase of a viral infection. Symptoms may start at an average of 5 days after exposure (for those that develop symptoms) with 97.5 % of people who develop symptoms that will have developed them within 11.5 days. A patient can be infectious two days before symptoms show.
PCR testing is a valuable tool to test close contacts of confirmed cases in the workplace and can be used to shorten quarantine times prior to starting work from the regular 10 to 14 days to less than a week without significantly increasing the risk of missing an infected person when compared to the risk at the end of a 14-day quarantine period. According to the CDC if you get tested on the fifth day after exposure or later and the result was negative, you can stop isolation after seven days.
#antigentest detect the presence of viral proteins (antigens) expressed by the COVID-19 virus in a sample from the respiratory tract of a person.
The antigen(s) detected are expressed only when the virus is actively replicating; therefore, these tests are best used to identify acute or early infection (up to 5 days from symptom onset).
Antigen tests are highly specific, but not as sensitive as PCR. This means there is a higher chance of false negatives.
Antigen test performance also depends on factors such as the time from onset of illness, the concentration of virus in the specimen, the quality of the specimen collected from a person, how it is processed, and the precise formulation of the reagents in the test kits.
Overall, in alignment with WORLD HEALTH ORGANIZATION (WHO) use of virus antigen tests is not recommended for diagnosis of SARS-CoV-2 infection. Antigen tests with >95 % specificity and >80 % sensitivity may be used for diagnosing infection with SARS-CoV-2, where no nucleic acid amplification tests are available or have prolonged turnaround times."