Rapid antigen tests (RATs) are popular tools for checking for viral infections because they give quick results and are easy to use. You can get results in just 15 to 30 minutes, and they can be used right where the patient is, which makes them really helpful in hospitals and clinics.

How Well Do They Work?

1. Sensitivity and Specificity:

   • For the virus that causes COVID-19 (SARS-CoV-2), RATs correctly identify about 72% of cases. They correctly show negative results around 98% of the time when compared to more accurate RT-PCR tests.
   • For influenza (the flu), RATs find 50% to 70% of cases correctly and show negative results around 90% to 95% of the time.

2. What This Means for Patients:

   • The high specificity (accuracy in identifying negatives) means there are fewer false positives - that means fewer wrong alerts saying someone is sick when they aren’t.
   • However, the lower sensitivity means some sick people might get missed, especially those who don’t have symptoms. In one study, RATs only detected 45% of COVID-19 cases in people with low amounts of the virus.

What Are the Drawbacks?

• RATs work less well for early infections or when the virus has changed a bit (like new variants).
• They shouldn’t replace more accurate tests when the results are really important, especially in serious medical cases.

In summary, RATs are great for giving quick results. But since they sometimes miss cases, it’s really important to follow up with more reliable tests to get a good diagnosis.