This is how the rapid COVID test should be repeated to rule out infection

A prospective cohort study, the largest of its kind on rapid tests to detect positives for COVID-19, has concluded that it may be necessary to repeat rapid antigen test (Ag-RDT) to rule out SARS-CoV-2 infection at 48-hour intervals. This means that people who are tested for SARS-CoV-2 should exercise caution in public places despite an initial negative result if they suspect they may be infected with or have been exposed to the coronavirus. The findings have been published in Annals of Internal Medicine.

Diagnostic tests for SARS-CoV-2 are an important component in the fight against COVID-19, since the appearance of rapid tests that can be bought in pharmacies and performed at home, we are all used to performing them the way suitable suitable. However the performance of this type of test for the detection of SARSCoV-2 in asymptomatic and symptomatic people it is not well established, they say from the American College of Physicians. In other words, should we trust a negative first result?

To clarify, researchers at the University of Massachusetts Chan School of Medicine studied 5,353 asymptomatic and SARS-CoV-2-negative participants to assess the performance of Ag-RDT. Participants were enrolled between October 2021 and January 2022, and completed Ag-RDT and PCR (reverse transcriptase polymerase chain reaction tests) for SARS-CoV-2 every 48 hours for 15 days. Ag-RDT tests were collected at home and reverse transcriptase polymerase chain reaction (RT-PCR) tests were sent to a central laboratory for analysis.

Rapid test performance was optimized when asymptomatic participants tested 3 times at 48-hour intervals and when symptomatic participants tested 2 times at the same interval.

The sensitivity of antigen tests it was measured on the basis of one test (on the same day), twice (after 48 hours) and three times (after 96 hours). Using the PCR test as a comparison, the data showed that the performance of the rapid test was optimized when asymptomatic participants tested 3 times at 48-hour intervals and when symptomatic participants tested 2 times at the same interval.

Las false positive rates they were low for rapid tests, suggesting that retesting is not necessary for those who test positive on the first or second try. Experts advise that while testing is underway, people should continue to practice mask wearing and social distancing until infection is ruled out.