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Coccidioidomycosis (Valley fever, San Joaquin Valley fever, Desert Rheumatism) is a caused by the dimorphic fungus Coccidioides immitis/posadasii, which is found in the southwestern United States and in Central and South America. It is acquired by inhalation of airborne Coccidioides arthroconidia. The majority of infections are subclinical. Among symptomatic patients, the majority will present acute flulike, pulmonary symptoms approximately 7 to 28 days post exposure, which may include chest pain, cough, fever, malaise, and lymphadenopathy.(1) A rash often develops within a couple of days, followed by erythema nodosum or multiforme with accompanying arthralgia. A pulmonary coin-like lesion or nodule may develop months following infection and may be a source of infection if the patient becomes immunosuppressed in the future. Coccidioidomycosis may disseminate beyond the lungs to involve multiple organs including the meninges. Individuals at greater risk for dissemination include African-Americans, patients of Filipino descent, pregnant women, and immunocompromised patients.(2)
Serologic testing for coccidioidomycosis should be considered when patients exhibit symptoms of pulmonary or meningeal infection and have lived or traveled in areas where Coccidioides immitis/posadasii is endemic. Any history of exposure to the organism or travel cannot be overemphasized when a diagnosis of coccidioidomycosis is being considered.
Screening for detection of antibodies to Coccidioides immitis/posadasii
A positive result is presumptive evidence that the patient was previously or is currently infected with Coccidioides immitis/posadasii. This specimen will be tested by complement fixation and immunodiffusion for confirmation.
A negative result indicates the absence of antibodies to Coccidioides immitis/posadasii and is presumptive evidence that the patient has not been previously exposed to and is not infected with Coccidioides. However, a negative result does not preclude the diagnosis of coccidioidomycosis as the specimen may have been drawn before antibodies levels were detectable due to early acute infection or immunosuppression. If infection is suspected, another specimen should be drawn in 7 to 14 days and retested to look for seroconversion.
This test is designed for the qualitative detection of both IgM- and IgG-class antibodies against antigens from Coccidioides. The report will not indicate which class of antibody is present.
This assay should not be used as a screen for the general population nor for monitoring response to therapy.
All results from this assay must be correlated with clinical history, epidemiologic data, and other laboratory evidence.
Positive results from this assay are not indicative of acute infection. Antibodies may be present from previous infection with Coccidioides immitis/posadasii.
Negative results may occur in patients with acute coccidioidomycosis in whom antibody levels have not yet become detectable.
Rarely, cross reactivity of the Coccidioides antibody screen may occur in patients infected with other dimorphic fungal agents including Histoplasma and Blastomyces. Therefore, all positive results must be confirmed by complement fixation and immunodiffusion.
1. Thompson GR: Pulmonary coccidioidomycosis. Semin Respir Crit Care Med 2011;32(6):754-763
2. Ruddy BE, Mayer AP, Ko MG, et al: Coccidioidomycosis in African Americans. Mayo Clin Proc 2011;86(1):63-69