Legionella Antigen Detection (Serum/Plasma)

Why This Test Matters

Legionnaires’ disease is a serious respiratory infection that can be life-threatening if untreated. While Legionella bacteria are common in water systems, symptoms like fever, cough, and shortness of breath can mimic other illnesses. This test helps doctors confirm a recent infection by identifying IgM antibodies, which appear shortly after exposure but fade over time.

What to Expect Before the Test

No special preparation is needed. You’ll provide a blood sample (usually drawn from your arm) in a serum or plasma tube. The sample is then sent to a lab for antibody detection using an immunoassay method.

What the Results Mean

A positive result suggests recent Legionella exposure and may indicate an active infection, though other causes of symptoms (like pneumonia from other bacteria or viruses) can’t be ruled out. A negative result means no detectable IgM antibodies at this time, but infection could still be present if symptoms persist.

When You Might Need This Test

Your doctor may order this test if you have symptoms like fever, cough, or chest pain—especially if you’ve traveled to areas with contaminated water, lived in a building with plumbing issues, or been in close contact with someone who has Legionnaires’ disease.