MYCPN - Clinical: Mycoplasma pneumoniae Antibodies, IgG and IgM, Serum

Test Catalog

Test Name

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

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

An aid in the diagnosis of disease associated with Mycoplasma pneumoniae

Testing Algorithm Delineates situation(s) when tests are added to the initial order. This includes reflex and additional tests.

If Mycoplasma pneumoniae antibodies, IgM is positive or equivocal, then Mycoplasma pneumoniae antibodies, 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 an important respiratory tract pathogen.


Several syndromes have been associated with the infection including pharyngitis, tracheobronchitis, pneumonia, and inflammation of the tympanic membrane presenting as bullous myringitis.  


Mycoplasma pneumoniae accounts for approximately 20% of all cases of pneumonia. Classically, it causes a disease that has been described as primary atypical pneumonia. The disease is of insidious onset with fever, headache, and malaise for 2 to 4 days before the onset of respiratory symptoms. Most cases do not require hospitalization. Symptomatic infections attributable to this organism most commonly occur in children and young adults (ages 2-19 years).(1)

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.


< or =0.90 (negative)

0.91-1.09 (equivocal)

> or =1.10 (positive)



< or =0.90 (negative)

0.91-1.09 (equivocal)

> or =1.10 (positive)


IgM by IFA

Negative (reported as positive or negative)

Interpretation Provides information to assist in interpretation of the test results

Positive IgM results are consistent with acute infection, although false positives do occur (see Cautions).


A single positive IgG result only indicates previous immunologic exposure.


Negative results do not rule-out the presence of Mycoplasma pneumoniae-associated disease. The specimen may have been drawn before the appearance of detectable antibodies. If testing is performed too early following primary infection, IgG and/or IgM may not be detectable. If a Mycoplasma infection is clinically indicated, a second specimen should be submitted in 14 to 21 days.

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

A diagnosis should not be made on the basis of antimycoplasma results alone. Test results should be interpreted in conjunction with the clinical evaluation and the results of other diagnostic procedures.


The use of hemolytic, lipemic, bacterially contaminated, or heat-inactivated specimens should be avoided as erroneous results may occur.


Assay performance characteristics have not been established for matrices other than serum.


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 Mycoplasma 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 Mycoplasma 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.


The prevalence of Mycoplasma IgM antibody is relatively low, which affects the assay's predictive value.

Supportive Data

The clinical study for this assay included 100 normal donor specimens that were tested for the presence of IgG and IgM class antibodies to Mycoplasma pneumoniae; 59% of the specimens contained IgG antibody and 4% displayed IgM antibody when tested with the EIA method.

Clinical Reference Provides recommendations for further in-depth reading of a clinical nature

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