What is the role of serological testing in the workup of Mycoplasma infections (Mycoplasma pneumoniae)?

Updated: Feb 15, 2019
  • Author: Ken B Waites, MD; Chief Editor: Michael Stuart Bronze, MD  more...
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Physicians use serology most frequently to confirm M pneumoniae infection even though these tests suffer from significant problems.

Many clinicians prefer enzyme-linked immunosorbent assays to the older, less sensitive complement fixation assays and nonspecific cold agglutinin titers. These types of tests are widely available through commercial reference laboratories.

Because primary infection does not guarantee protective immunity against future infections and residual immunoglobulin G (IgG) may remain from earlier encounters with the organism, experts have launched a great impetus to develop sensitive and specific tests that can differentiate between acute and remote infection.

Definitive diagnosis requires seroconversion documented by paired specimens obtained 2-4 weeks apart. Although some researchers purport that single-titer immunoglobulin M (IgM) or immunoglobulin A (IgA) assays reveal current infection, IgM may persist for up to several months in some people, and many adults may not mount a detectable IgM response. Therefore, relying on a single serological test can be clinically misleading, and experts recommend basing diagnosis of acute infection on seroconversion measured simultaneously in assays for both IgM and IgG. Use of serology for diagnosis of mycoplasmal infection is valid only if the patient has a satisfactory capacity of the humoral immune system to mount an antibody response.

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