GenBody Mycoplasma Ag

Abstract

Direct and indirect antigen-capture enzyme immunoassays (Ag-EIA) have been developed for the detection of Mycoplasma pneumonia in nasopharyngeal aspirates or sputum from a respiratory infection. The sensitivity of the two Ag-EIAs was similar, but the indirect method using polyclonal rabbit and guinea pig antisera was more convenient. The Ag-EIA had a detection limit of 10 (4-4.5) colony-forming units/ml of sample. It was specific for M. pneumoniae and gave a low-level response with M. genitalium. There were no cross-reactions with 10 other mycoplasma species.

Tests with a wide range of bacteria and antigens from the chlamydia group, representing agents sometimes found in the respiratory tract, were also negative. At the current level of development, the Ag-EIA detected about 90% of the samples that were also positive for culture; 43% of the samples from seropositive patients with a negative culture gave a positive result. The general pattern of results indicated that, while antigen detection is a rapid and effective substitute for the slow culture method, serological examination for specific IgM antibodies is also necessary to provide comprehensive diagnostic coverage.

Test algorithm

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

Mycoplasma pneumonia is a small bacteria transmitted through droplets that contain organisms. It is a cause of upper respiratory infection, pharyngitis, and tracheobronchitis, particularly in children, and has been associated with approximately 20% of community-acquired pneumonia cases. Cardiac and central nervous system manifestations are probably the most common extrapulmonary complications of M. pneumoniae infections. The disease is usually self-limited, although the severe disease has been reported in immunosuppressed patients.

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

Reference values

  • IgG: negative
  • IgM: negative
  • IgM by IFA: negative

Cautions

  • The diagnosis of Mycoplasma pneumoniae infection should not be based solely on the results of serological tests for this agent. Test results should be interpreted in conjunction with clinical evaluation and the results of other diagnostic procedures (eg, molecular screening).
  • The continued presence or absence of antibodies cannot be used to determine the success or failure of therapy.
  • The tests should not be performed as a screening procedure for the general population. Testing should only be performed when clinical evidence suggests the diagnosis of M. pneumoniae-associated disease.
  • The performance of this test in neonates and immunosuppressed patients has not been established.
  • The performance of the IgM assay has not been tested with samples known to be positive for antibodies against organisms known to be associated with lower respiratory diseases (i.e. influenza A and B, cytomegalovirus, Chlamydophila pneumonia, parainfluenza ) and known closely related serovars. to cross-react with M. pneumonia, such as Mycoplasma genitalium and Mycoplasma hominis, as well as with various species of Ureaplasma. No cross-reactivity studies have been performed with these organisms with this assay.
  • The IgG Removal System included with the IgM Test System has been shown to functionally remove IgG from samples containing total IgG levels ranging from 300 to 600 mg/ml. The efficacy of this clearance system at IgG levels above 600 mg/ml has not been established.

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