Flu (Influenza) Test

The flu (influenza) test is a diagnostic tool used to determine if a person has influenza, commonly known as the flu. The test can help identify the presence of the influenza virus in the body and distinguish it from other respiratory illnesses.

Types of Flu Tests

• Rapid Influenza Diagnostic Tests (RIDTs): These tests provide quick results, usually within 15-30 minutes. They can detect influenza A and B viruses but may not be as accurate as other tests.
• Reverse Transcription Polymerase Chain Reaction (RT-PCR) Tests: These tests are more sensitive and specific than RIDTs. They can identify the genetic material of the influenza virus and provide results within several hours.
• Immunofluorescence Assays: These tests use a fluorescent dye to detect the presence of influenza viruses in respiratory samples. They are often used in combination with other tests.
• Viral Culture Tests: These tests involve growing the influenza virus in a laboratory setting. While they can provide accurate results, they may take several days to complete.

How the Test is Performed

The flu test typically involves collecting a sample of respiratory secretions, such as:

• Nasal swab: A healthcare professional inserts a swab into the nostril to collect a sample from the nasal passage.
• Throat swab: A healthcare professional inserts a swab into the throat to collect a sample from the tonsils and surrounding area.

When to Get Tested

The Centers for Disease Control and Prevention (CDC) recommend getting tested for influenza if:

• You have symptoms of the flu, such as fever, cough, sore throat, runny or stuffy nose, muscle or body aches, headaches, fatigue, and vomiting or diarrhea.
• You are at high risk for complications from the flu, such as older adults, young children, pregnant women, and people with certain chronic health conditions.

Interpreting Test Results

A positive test result indicates that the influenza virus is present in the body. A negative test result does not necessarily mean that you do not have the flu, as some tests may not detect the virus. If your healthcare professional suspects that you have the flu based on your symptoms and medical history, they may prescribe antiviral medication even if the test result is negative.

Limitations of Flu Tests

Flu tests are not 100% accurate and may have limitations, such as:

• False-negative results: The test may not detect the influenza virus even if it is present.
• False-positive results: The test may indicate that the influenza virus is present when it is not.