Home tests can detect new COVID variant, but may take longer

In recent months, there have been reports of individuals experiencing COVID-19 symptoms but testing negative for the virus. This has raised concerns about the accuracy of at-home antigen tests and whether they can detect the new dominant variant, JN.1. However, infectious disease experts propose an alternative explanation for these delayed positive results: our immune systems have become more efficient at recognizing the virus.

As the pandemic has progressed and a large portion of the population has either been infected or vaccinated, our immune systems have become better at alerting us to the presence of the virus. This means that symptoms may appear earlier in the course of the infection compared to earlier in the pandemic. However, during the initial days of infection, the viral load may not be high enough for at-home antigen tests to detect, resulting in a negative result.

Dr. Peter Chin-Hong, an infectious disease specialist, believes that future variants are unlikely to further delay the onset of symptoms. This phenomenon of delayed positive results has been observed with other variants as well, as the population gains immunity through natural infections and vaccinations.

A study published in Clinical Infectious Diseases supports this theory, showing that viral load peaks around the fourth day of symptoms in individuals with a high level of immunity. The sensitivity of at-home tests is expected to be highest during this period, although some individuals may still test positive earlier.

The Centers for Disease Control and Prevention (CDC) recommends testing immediately if symptoms are present. If an at-home test is negative, individuals are advised to retest after 48 hours or opt for a PCR test. For those without symptoms but with potential exposure, the CDC suggests waiting 5 days before testing. If the initial at-home test is negative, individuals can retest after 48 hours or choose a PCR test.

Repeat testing can be challenging and costly, but it is important for making treatment and other decisions. The research does not discourage testing, but rather emphasizes the need for multiple tests to ensure accuracy. The decision to test immediately or wait depends on individual circumstances and access to testing options.

In conclusion, delayed positive results on at-home antigen tests may be due to our immune systems becoming more efficient at detecting the virus. While repeat testing is recommended for accuracy, individuals should consult CDC guidelines and consider their personal circumstances when making testing decisions.


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