What is the role of serology in the workup of mycoplasmal pneumonia?

Updated: Dec 28, 2018
  • Author: Michael Joseph Bono, MD, FACEP; Chief Editor: Guy W Soo Hoo, MD, MPH  more...
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Answer

Serum cold agglutination is a nonspecific test for M pneumoniae, but findings are positive in only 50-70% of patients after 7-10 days of infection. Cold agglutinin tests can be obtained from diagnostic laboratories. A negative result does not exclude infection, and this test may be affected by cross-reactions with other pathogens, such as adenovirus, Epstein-Barr virus, and measles viruses. A quick bedside test can be performed by partially filling a purple-top tube with blood and placing it in ice. A positive finding is one in which "grains of sand" appear on the glass portion of the tube.

Serology tests that demonstrate a 4-fold or greater increase or decrease in paired sera titers or a single titer greater than or equal to 1:32 supports the diagnosis of mycoplasmal pneumonia. Serologic tests include complement fixation, enzyme-linked immunoassay, immunochromatography, [31] and indirect hemagglutination. [32] All of these have acceptable sensitivity and specificity.

Optimized serodiagnosis of M pneumoniae using a new set of antigens has shown comparable sensitivity to positive real-time polymerase chain reaction (PCR) results. [33]


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