Influenza B Virus IgG Antibody Titer, Serum

What This Test Measures

The test detects and quantifies IgG-class antibodies directed against influenza B virus in your blood serum. IgG antibodies generally appear after infection or vaccination and can persist for months to years, so this measurement is primarily a marker of past exposure or immune response rather than of current illness.

How the Sample Is Collected

A healthcare professional collects a blood sample from a vein in your arm into a tube, and the serum is separated in the laboratory for testing. No special preparation is usually required unless your provider gives other instructions. The antibody level is then measured, often by comparing the reactivity of your sample against a standard to produce a titer.

What the Results Mean

Results are reported as a titer, which indicates how much your serum can be diluted and still show detectable antibody. A higher titer generally suggests greater antibody levels from past infection or vaccination. Because antibody levels vary widely between individuals and testing methods differ between laboratories, results are best interpreted by your healthcare provider in the context of your history, symptoms, and vaccination status.

Limitations to Keep in Mind

This test does not reliably tell you whether you currently have influenza, and a negative or low result does not necessarily mean you are unprotected. Antibody levels can wane over time, and cross-reactivity or differences in laboratory methods can affect results. It is not a substitute for tests that directly detect the virus during an active infection.