The IgG antibody test against Mycoplasma pneumoniae is used to detect mycoplasma infection. IgG antibody titres rise after 3-4 weeks. from the start of infection. During an acute infection, antibody levels exceed the normal range by 4-5 times. IgG antibodies are reduced after infection, but can still be detected in serum for several years.

To diagnose and confirm a mycoplasma infection, the test should be repeated after 2-3 weeks. since the first test to assess antibody dynamics and changes in the body.

IgG is an airborne droplet that infects the mucous membranes of the respiratory tract. These infections can cause pharyngitis, laryngitis and sinusitis. A dry, persistent cough is the most common symptom of these infections. Not everyone with mycoplasma and chlamydia in their nasopharynx will get sick – it depends on the body’s resistance – but they can infect others.

Antibodies in the blood appear later than IgM antibodies, 3-4 weeks after infection. Mycoplasma pneumoniae IgG antibodies are produced in the event of a re-infection.

Clinical Significance

Mycoplasma pneumoniae Antibodies (IgG, IgM) –

This test helps detect Mycoplasma pneumoniae infections. Respiratory tract infections including community-acquired pneumonia are common reasons for testing for M pneumoniae, especially in children [3,4].

Clinical presentations of M pneumoniae infection are generally mild, but can vary widely across individuals, and are most often characterized by tracheobronchitis with upper respiratory tract symptoms. Approximately one-third of people with M pneumoniae infection develop pneumonia that was previously considered “atypical.” Extrapulmonary complications may include encephalitis, hemolytic anemia, renal dysfunction, gastrointestinal complaints, erythema multiforme, and Stevens-Johnson syndrome [1,2].

M pneumoniae infection is diagnosed by culture, serology, or nucleic acid amplification tests. Serologic tests may be useful when the possibility of Mycoplasma infection is high. A positive IgG result indicates previous or recent infection. Testing children who have suspected community-acquired pneumonia for M pneumoniae may help guide antibiotic selection [3,4].

Clinical false-negative results for IgG- and IgM-based serologic tests can occur due to compromised immunity, testing before an antibody response has started, or the presence of interfering substances in host serum.

Real-time polymerase chain reaction testing for M pneumoniae DNA is more sensitive than serology testing and can provide timely results to inform patient management [2]. IgA antibodies to M pneumoniae appear early; testing IgA antibodies may aid in identifying acute infection [1].

The results of this test should be interpreted in the context of pertinent clinical history and physical examination findings.

References
1. Waites KB, et al. Mycoplasma and Ureaplasma. In: Carroll KC, et al, eds. Manual of Clinical Microbiology. 12th ed. ASM Press; 2019. https://www.clinmicronow.org/doi/book/10.1128/9781683670438.MCM.ch64
2. Centers for Disease Control and Prevention. Mycoplasma pneumoniae Infections. Last reviewed June 5, 2020. Accessed January 27, 2022. https://www.cdc.gov/pneumonia/atypical/mycoplasma/hcp/index.html
3. Miller JM, et al. Clin Infect Dis. 2018;67(6):813-816.
4. Bradley JS, et al. Clin Infect Dis. 2011;53(7):617-630.

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