Rapid diagnostic tests are helpful in identifying someone who is contagious, but may or may not be showing symptoms, so they can take action before they spread the virus to others. Rapid tests can be done at-home and they are easy to use for quick results. While at-home testing kits are swift in delivering results and cost-effective, there can be possibilities of getting a false positive or a negative result.

A COVID-19 test kit either shows two lines next to the letters C and T suggesting a positive result or displays only one line next to C, suggesting a negative COVID result. However, if you notice very faint lines on the testing device, you might find it difficult to interpret the same and chances of a false negative or positive may be high.

According to medical experts, rapid antigen tests for COVID-19 work only when manufacturer instructions are followed. COVID-19 test kits approved by health authorities for usage in Viet Nam are recommended for the public to use at home amid a surge in COVID-19 cases.

Medical experts recommend carefully reading all the manufacturer's instructions when taking an at-home COVID-19 test and reading the test results only within the time frame specified in the instructions. If you don't follow the instructions, your test results could be incorrect. Reading the results too soon may turn up a false-negative result because the test didn’t have time to properly process your sample but reading the results too late may give you a false-positive result.

False-positives are possible due to the timing of the test (ie, too early or too late in the infectious stage). Rapid tests are sensitive enough to detect cases with high viral load, early in the course of infection in pre-symptomatic and early symptomatic cases up to five days from symptom onset. Rapid antigen tests in people with COVID-19 symptoms found sensitivities but these tests have a tendency to generate some false-positive results in asymptomatic people.

You should follow the instructions for the test and avoid eating or drinking for at least 30 minutes before you take it, blow your nose beforehand and remember to wash your hands and read the results at the exact time recommended in order to have a much better chance of getting a reliable result.

Reporting by H.D – translating by H.L