Legionella Antigen Detection by Immunoassay (Serum)

Why This Test Might Be Ordered

Your healthcare provider may recommend this test if you’ve recently had symptoms like fever, cough, shortness of breath, or chest pain—especially if you’ve traveled to areas with known Legionella outbreaks, lived in or visited a building with plumbing issues, or been exposed to contaminated water. It’s also used for screening in high-risk groups, such as those with weakened immune systems or chronic lung conditions.

What to Expect Before the Test

No special preparation is needed. You’ll have a small needle inserted into your arm to draw blood. The sample is processed in our lab to detect specific antibodies related to Legionella. Results are typically available within 24–48 hours.

What the Test Results Mean

A positive result suggests recent infection, but it doesn’t confirm Legionella alone—other tests (like culture or PCR) may be needed. A negative result means no detectable IgM antibodies at the time of testing, but infection could still be present if symptoms persist. False positives are rare but possible.

Common Causes of False Results

False positives can occur if you’ve had a recent vaccination, exposure to other infections, or if the test was misinterpreted. False negatives may happen if the infection was recent or if the test was taken too early. Your provider will discuss results in context with your symptoms and medical history.