What is the role of immunoglobulin G (IgG) detection in the workup of coccidioidomycosis?

Updated: Aug 27, 2019
  • Author: Duane R Hospenthal, MD, PhD, FACP, FIDSA, FASTMH; Chief Editor: Michael Stuart Bronze, MD  more...
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Answer

Immunodiffusion and complement fixation (CF) methods can detect coccidioidal immunoglobulin G (IgG). IgG antibodies detected via CF become positive in 85-90% of patients by 3 months after infection onset, persist 6-8 months, and disappear as infection resolves. However, in some cases IgG can persist for years.

In contrast to IgM, for which quantification is uninformative, the CF titer is useful as a quantitative measure of the extent and progression of disease. The CF IgG titer may be low or absent in mild or asymptomatic disease or in immunosuppressed patients. Approximately 95-100% of patients with titers of 1:16 or less do not have disseminated disease. High titers (ie, 1:32 or higher) persist in severe, untreated extrapulmonary or disseminated disease.

Coccidioidal CF titers in the serum and cerebrospinal fluid can be followed to monitor the effect of treatment on disease and predict relapses.


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