At-home health testing offers a convenient way to identify common respiratory illnesses. Home flu tests are available, allowing individuals to test for influenza outside a clinical setting.
Availability and Function of Home Flu Tests
Home flu tests are available at pharmacies or online. Many are combination kits designed to detect not only influenza A and B viruses but also SARS-CoV-2, the virus responsible for COVID-19, from a single sample. These tests typically utilize a nasal swab for sample collection, which users perform themselves following the kit’s instructions.
The most common type of home flu test is a rapid antigen test. These tests work by identifying specific viral proteins, known as antigens, in respiratory fluid. After sample collection, it is mixed with a reactive liquid and applied to a test strip. Viral antigens then trigger a visual change, like colored lines, within 10 to 30 minutes, indicating a positive result. Some home tests are molecular assays, which are generally more accurate as they detect the genetic material of the flu virus, though results may take longer if the sample needs to be mailed to a laboratory.
Accuracy and Considerations for Home Flu Tests
Home flu tests, particularly rapid antigen tests, are characterized by their sensitivity and specificity. Sensitivity measures a test’s ability to correctly identify individuals who have the flu, while specificity indicates its ability to correctly identify those who do not. Rapid antigen tests generally exhibit moderate sensitivity, ranging from approximately 50% to 70%, meaning they can miss actual flu cases, leading to false negative results. Conversely, their specificity is typically high, often around 95% to 99%, so false positive results are rare.
Accuracy is influenced by several factors. The timing of the test relative to symptom onset plays a significant role; tests are most accurate when performed within the first 48 to 72 hours of symptoms appearing, as this is when viral load is usually highest. Improper sample collection, such as not swabbing far enough into the nose, can also lead to inaccurate results. Additionally, these rapid tests can detect influenza A and B but do not differentiate between specific strains. Home flu tests generally do not identify other respiratory viruses that might cause similar symptoms, such as RSV, unless it is a multi-target test.
What to Do After a Home Flu Test
Interpreting home flu test results requires careful consideration. A positive flu test result indicates the flu virus is highly probable. Individuals should contact a healthcare provider promptly, especially if they are at higher risk for severe illness or complications. Antiviral medications can be prescribed to lessen symptoms and potentially shorten the duration of illness, but they are most effective when started within 48 hours of symptom onset.
Regardless of antiviral treatment, individuals with a positive result should isolate themselves to prevent further spread of the virus. Staying home from work or school, getting ample rest, and staying hydrated are important for recovery. Practicing good hygiene, such as frequent handwashing and covering coughs and sneezes, is also advised. Individuals should remain isolated until their fever has resolved for at least 24 hours without fever-reducing medication and their symptoms are improving.
A negative home flu test result is considered presumptive; moderate sensitivity means a false negative is possible, especially if performed too early or late in the illness course. If symptoms persist or worsen, retest in 48 hours or seek medical consultation. A healthcare provider can determine if a more sensitive laboratory-based test, such as a PCR test, is necessary or if another respiratory illness might be the cause of symptoms. Seek emergency care if severe symptoms develop, such as difficulty breathing, persistent chest pain or pressure, sudden dizziness, confusion, or severe or persistent vomiting.