When symptoms like a cough, fever, and body aches appear, many people wonder if they have the flu or a common cold. At-home testing offers rapid insights, helping individuals decide whether to seek medical care or manage symptoms at home.
Over-the-Counter Flu Tests Are Available
Over-the-counter (OTC) flu tests are available, typically as rapid antigen tests designed to detect specific proteins from influenza A and B viruses. Some newer tests also combine detection for influenza A and B, and SARS-CoV-2 (the virus that causes COVID-19), from a single nasal swab. These combination tests became widely available last flu season, providing a convenient option for identifying common respiratory viruses.
These tests are available at retail pharmacies and online retailers. The cost for a rapid antigen test for flu and COVID-19 can be as low as $13, though prices may vary. The U.S. Food and Drug Administration (FDA) has authorized these at-home diagnostic tests for over-the-counter use, making them accessible without a prescription.
Using an At-Home Flu Test
Using an at-home flu test involves a few straightforward steps, but always follow the specific instructions provided with each kit. Begin by washing your hands thoroughly and setting up a clean, flat surface. The main step involves collecting a nasal swab sample. For adults, this means inserting the swab about 1 to 1.5 inches into one nostril, gently rotating it against the nasal wall several times, then repeating the process in the other nostril with the same swab.
After collecting the sample, the swab is inserted into a provided solution or test tube and swirled to mix. The liquid is then squeezed from the swab, and a few drops are added to a designated well on the test device. Results are available within 10 to 30 minutes, depending on the specific test. For most accurate results, use the test within the first few days of symptom onset, ideally within 48 to 72 hours.
Interpreting Test Results and Their Limitations
When interpreting at-home flu test results, a positive result appears as a colored line or lines on the test device, indicating the presence of influenza A, influenza B, or both (and possibly COVID-19 if it’s a combination test). A negative result shows only a control line, suggesting no viral antigens were detected. While a positive result can be trusted, a negative result does not completely rule out the illness.
Rapid antigen tests have limitations, particularly concerning their sensitivity compared to laboratory-based molecular tests. Rapid influenza diagnostic tests (RIDTs) have sensitivities ranging from 50% to 70%, meaning they may miss true flu infections. Specificity, the test’s ability to correctly identify those without the virus, is higher, 90% to 95%. False negative results are more common than false positives, especially if the test is performed more than 72 hours after symptoms begin or if the viral load is low. Therefore, a negative result should be interpreted with caution, and a positive result should prompt a discussion with a healthcare provider to consider treatment options.
When to Seek Professional Medical Advice
Knowing when to consult a healthcare provider is important, even with an at-home flu test result. If you test positive for flu, contact a medical professional. Antiviral medications are most effective when started within 48 hours of symptom onset. Your doctor can discuss symptom management and determine if antiviral treatment is suitable.
Regardless of your test result, seek medical attention if you experience severe symptoms such as difficulty breathing, shortness of breath, chest pain, sudden dizziness, or confusion. Worsening symptoms, or symptoms that improve and then return with fever and a worse cough, also warrant medical consultation. Individuals in high-risk groups, including young children, adults over 65, pregnant individuals, and those with chronic medical conditions like asthma, diabetes, or heart disease, should contact their healthcare provider as soon as flu symptoms develop.