Serum Immunoassay for Immunoglobulin M (IgM) Antibodies Against *Mycoplasma pneumoniae*
This test measures the level of IgM antibodies in your blood that your immune system produces in response to an infection by *Mycoplasma pneumoniae*, a common cause of atypical pneumonia.
["Detects recent *Mycoplasma pneumoniae* infection via IgM antibodies."]
Key facts at a glance
- LOINC
- 42494-5
- Short code
- C immitis Ab Titr Plr CF
- Synonyms
- C immitis Ab Titr Plr CF
- Category
- chemistry
- Sample
- fluid
- Container
- Sterile tube
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- comp-fix
- Specimen volume
- 2-5 mL
- Stability
- Room temperature: 2h, Refrigerated: 24h
- Hemolysis max
- 300
- TAT
- 4–24 hours
- Order
- routine
What This Test Measures
IgM antibodies are part of your immune system’s early response to infection. This test checks for these antibodies to help identify if you’ve recently been exposed to *Mycoplasma pneumoniae*, which can cause respiratory symptoms like coughing, fever, or chest pain. IgM levels typically rise within weeks of infection and can stay elevated for months.
Why It Might Be Ordered
Your doctor may recommend this test if you have symptoms of pneumonia (such as persistent cough, shortness of breath, or fatigue) that don’t improve with typical antibiotics, or if you’ve been exposed to someone with *Mycoplasma pneumoniae* infection. It’s also used in cases where other causes of pneumonia are suspected.
What to Expect Before the Test
No special preparation is needed. You’ll provide a blood sample, usually drawn from your arm. The test is quick and typically done in a lab setting. Avoid alcohol for 24 hours before testing if instructed by your healthcare provider, as it may affect results.
What the Results Mean
A positive result indicates recent infection with *Mycoplasma pneumoniae*, as your body has produced IgM antibodies in response. A negative result suggests either no recent infection or that the IgM antibodies have already declined (meaning you may have recovered). False negatives can occur if tested too early after exposure.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
◆Associated findings1
Short name
IgM Anti-*Mycoplasma pneumoniae* (Serum)
Frequently asked questions
This test helps confirm a diagnosis of *Mycoplasma pneumoniae* pneumonia, which can be difficult to identify without specific testing. Early detection is important because symptoms can mimic other infections, and treatment with appropriate antibiotics (like azithromycin) is crucial for recovery.
Can I get this test at home? No, this is a blood test that requires a medical professional to collect the sample in a clinical setting.
Does this test cover other infections? No, this test is specific for *Mycoplasma pneumoniae*. If you suspect another type of infection, your doctor may order different tests.
Sources
- 1
- 2Lab Tests OnlineSource
- 3
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.
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