Influenza Virus Nucleoprotein Antibody, Qualitative Immunoassay (Serum/Plasma)

This test measures antibodies against influenza viruses in a sample of your blood. Antibodies are proteins your immune system makes to fight the flu, and their presence can show whether you have been exposed to influenza or have responded to a flu vaccine in the past.

The test looks for specific antibodies (proteins) your body produces in response to exposure to influenza viruses. These antibodies indicate whether you’ve had an infection or been vaccinated. The result is qualitative—meaning it only tells you if antibodies are present (positive) or not (negative).

Your doctor may order this test to confirm a previous flu infection, evaluate how your immune system is responding, check whether a flu vaccine produced an adequate antibody response, or help investigate a suspected outbreak within a community or workplace.

Healthcare providers may order this test if you’ve had symptoms of flu (like fever, cough, or body aches) and suspect exposure, especially if you’re at higher risk for complications. It can also help confirm if a previous flu infection has affected your immune response or if vaccination was effective.

A healthcare professional will draw a small blood sample from a vein, usually in your arm. No fasting or special diet is required beforehand, but tell your provider about any medications or supplements you take, and mention any recent illness, fever, or vaccination dates.

A blood sample is drawn from a vein in your arm. The blood is processed into either serum (liquid after clotting) or plasma (liquid after centrifugation). The test uses an immunoassay method to detect antibodies without measuring exact amounts.

A positive result means flu antibodies were found, which usually indicates a past influenza infection or a response to vaccination. A negative result means no antibodies were detected. Sometimes two samples taken a week or two apart are compared to see whether antibody levels rose over time.

A positive result means antibodies to the influenza virus are present, suggesting past infection or vaccination. A negative result means no detectable antibodies were found. Results don’t indicate the current illness status or virus type.