Influenza Test
Detects influenza A and B viruses.
Content last reviewed 2026-09-12 · Educational information — not medical advice
It is commonly considered when evaluating Influenza; people with Cough, Fatigue, Fever may have it ordered as part of their work-up.
What is the Influenza Test?
The Influenza Test uses clinical microbiology methods to look for evidence of infection or immunity.
Background: What is the flu? The flu, also called influenza, is a respiratory infection caused by viruses. Each year, millions of Americans get sick with the flu. Sometimes it causes mild illness. But it can also be serious or even deadly, especially for people over 65, newborn babies, and people with certain chronic illnesses. What causes the flu? The flu is caused by flu viruses that spread from person to person. When someone with the flu coughs, sneezes, or talks, they spray tiny droplets. These droplets can land in the mouths or noses of people who are nearby. Less often, a person may get flu by touching a surface or object that has flu virus on it and then touching their own mouth, nose, or possibl…
How the Influenza Test works
Methods vary by pathogen: antibody serology detects your immune response (IgG/IgM), antigen tests find pathogen proteins, NAAT amplifies pathogen genetic material, cultures grow the organism, and microscopy inspects specimens directly.
Why healthcare providers order it
Ordered when exposure history, symptoms, travel, or screening protocols raise the question of a specific infection — and for immunity checks (titers) before school, work, pregnancy, or after vaccination.
Interpreting your results
Understanding infectious-disease results
- IgG positive: past infection or vaccination — usually immunity.
- IgM positive: suggests recent/active infection, though IgM can persist and false positives occur; confirmatory testing is standard.
- Antigen/NAAT positive: direct detection of the pathogen — active infection.
- Culture positive: organism grown and identified; sensitivity testing guides antibiotic choice.
- Negative: no detection, subject to window periods and specimen quality.
Reference intervals vary by laboratory, instrument, age, sex, and — for hormones — collection time. Always compare your value against the range printed on your own report, and review results with a qualified healthcare professional who knows your history. This guide is educational and does not diagnose.
Understanding your lab report
- Find the reference interval printed beside your value on the report — that pairing defines 'normal' for this lab run.
- Note the units. mmol/L vs mg/dL, ng/mL vs µg/L — numbers mean nothing across unit systems.
- Look at flags (H/L) but read the degree: barely-outside values behave differently than multiples of the limit.
- Trends outrank snapshots. A series of results tells your provider far more than any single draw.
Conditions that may involve Influenza Test
Symptoms that may lead to this test
Frequently asked questions
What does the Influenza Test measure?
It quantifies a specific biomarker or characteristic of the submitted sample, compared against a laboratory-defined reference interval.
Do I need to fast before the Influenza Test?
Fasting is not routinely required for this test; follow any instructions from your provider or laboratory.
How soon do Influenza Test results come back?
Most routine assays return within 1–3 business days; specialty methods can extend that to a week or more.
Can an abnormal Influenza Test result mean something serious?
Many of these infections are treatable; a positive result is interpreted with your symptoms, exposure history, and confirmatory testing.
Sources & data provenance
- MedlinePlus — 'Flu' (https://medlineplus.gov/flu.html)
- Family-specific guidance compiled from standard clinical laboratory medicine references