Skip to content

Legionella Antibody Serology (Serum/Plasma)

Published: August 9, 2026Updated: August 16, 2026

This test detects antibodies in your blood that may indicate past or current exposure to *Legionella*, a type of bacteria found in water systems that can cause severe respiratory illness.

Quick summary

["Helps identify possible Legionnaires’ disease exposure by checking for immune system response."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
38392-7
Short code
Legionella Ab Ser Ql
Synonyms
Legionella Ab Ser Ql
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

Why This Test Might Be Ordered

Your healthcare provider may recommend this test if you’ve had symptoms like coughing, shortness of breath, or fever—especially after recent travel to areas with contaminated water sources, exposure to cooling towers, or contact with someone who has Legionnaires’ disease. It may also be used in outbreaks or if you’ve been exposed to Legionella in your environment.

What to Expect Before the Test

No special preparation is needed. You’ll provide a blood sample (usually from a vein in your arm) by a phlebotomist. The sample is then sent to a lab for antibody detection.

What the Results Mean

Positive results suggest your immune system has recognized Legionella, but they don’t confirm active infection. Negative results mean no detectable antibodies were found at this time. Results may take several days to weeks to return, depending on the lab.

Possible Limitations

Antibodies take time to develop after exposure, so a negative result doesn’t always rule out past or recent infection. False positives can occur rarely, and results may vary if you’ve recently been vaccinated or had a blood transfusion.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

Legionella Antibody Test

Frequently asked questions

What Does This Test Detect?
This test detects *Legionella* antibodies (IgG and IgM) in your serum or plasma. IgM appears early in infection but fades quickly, while IgG persists longer and indicates past exposure. The test is qualitative, meaning it only shows presence or absence of antibodies, not exact levels.
When Might This Test Be Used?
This test is often used in outbreaks, environmental investigations, or when Legionnaires’ disease is suspected but culture results are pending. It’s not a first-line diagnostic tool for active infection but can help guide further testing or public health efforts.
How Does This Test Differ from Culture?
Unlike culture (which grows bacteria to confirm infection), this test only detects your immune response. Culture is more accurate for diagnosing active Legionnaires’ disease but takes longer and may not always identify the bacteria.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy