Test Catalog

Test ID: MYCO    
Mycoplasma pneumoniae Antibodies, IgG and IgM, Serum

Useful For Suggests clinical disorders or settings where the test may be helpful

Screening for recent or past exposure to Mycoplasma pneumoniae


This test should not be used as a screening procedure for the general population.

Testing Algorithm Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

If Mycoplasma pneumoniae, IgM is reactive or equivocal, then M pneumoniae IgM by indirect immunofluorescence assay (IFA) will be performed at an additional charge.

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Mycoplasma pneumoniae is a small bacterium transmitted via organism-containing droplets. It is a cause of upper respiratory infection, pharyngitis, and tracheobronchitis, particularly in children, and has been associated with approximately 20% of cases of community-acquired pneumonia. Central nervous system and cardiac manifestations are probably the most frequent extrapulmonary complications of infections due to M pneumoniae. The disease is usually self-limited, although severe disease has been reported in immunocompromised patients.


Identification of M pneumoniae by culture-based methods is time consuming and insensitive. Serology-based assays for M pneumoniae have several drawbacks. The development of IgM antibodies takes approximately 1 week and the IgM response in adults may be variable or it may be decreased in immunosuppressed individuals. Confirmation of the disease is dependent on the observation of a 4-fold rise in IgG antibody titers between acute and convalescent specimens, several weeks following the initial onset of illness, providing clinical utility only for retrospective testing. Real-time PCR offers a rapid and sensitive option for detection of M pneumoniae DNA from clinical specimens allows for diagnosis of acute or current infection.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

IgG: negative

IgM: negative

IgM by IFA: negative

Interpretation Provides information to assist in interpretation of the test results

IgG ELISA Result

IgM ELISA Result




Results suggest past exposure.




Prior exposure to Mycoplasma pneumoniae detected. Confirmatory testing for IgM to M pneumonia will be performed by an immunofluorescence assay.




No antibodies to M pneumoniae detected. Acute infection cannot be ruled out as antibody levels may be below the limit of detection.  If clinically indicated, a second serum should be submitted in 14 to 21 days.



No prior exposure to Mycoplasma pneumoniae. Confirmatory testing for IgM to M pneumonia will be performed by an immunofluorescence assay..




Recommend follow-up testing in 10 to 14 days if clinically indicated.


Confirmatory testing for IgM to M pneumonia will be performed by an immunofluorescence assay.


ELISA = Enzyme-linked immunosorbent assay

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

A diagnosis of Mycoplasma pneumoniae infection should not be solely based on results of serologic testing for this agent. Test results should be interpreted in conjunction with clinical evaluation and the results of other diagnostic procedures (eg, molecular detection).


The continued presence or absence of antibodies cannot be used to determine the success or failure of therapy.


Testing should not be performed as a screening procedure for the general population. Testing should only be done when clinical evidence suggests the diagnosis of M pneumoniae-associated disease.


The performance of this test has not been established on neonates and immunocompromised patients.


Performance of the IgM assay has not been tested with specimens known to be positive for antibodies to organisms that are known to be associated with lower respiratory illness (ie, influenza A and B, cytomegalovirus, Chlamydophila pneumoniae, parainfluenza), and closely related serovars known to cross-react with M pneumoniae, such as Mycoplasma genitalium and Mycoplasma hominis, as well as various Ureaplasma species. Cross-reactivity studies with such organisms have not been performed with this assay.


The IgG removal system included with the IgM test system has been shown to functionally remove the IgG from specimens containing total IgG levels ranging from 300 to 600 mg/mL. The effectiveness of this removal system at IgG levels exceeding 600 mg/mL has not been established.

Clinical Reference Recommendations for in-depth reading of a clinical nature

1. Smith T: Mycoplasma pneumoniae infections: diagnosis based on immunofluorescence titer of IgG and IgM antibodies. Mayo Clin Proc. 1986;61:830-831

2. Holzman RS, Simberkoff MS, Leaf HL: Mycoplasma pneumoniae and atypical pneumonia. In Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 9th ed. Elsevier; 2020:2332-2339