infectious diseases
Coccidioidomycosis
Diagnosis of Coccidioidomycosis
Cultures (routine or fungal) Microscopic examination of specimens to check forC. immitisspherules Serologic testing Eosinophilia may be an important clue in identifying coccidioidomycosis. The diagnosis of coccidioidomycosis is suspected based on history and typical physical findings, when apparent; chest x-ray findings can help confirm the diagnosis, which can be established by fungal culture or by visualization ofC. immitisspherules in sputum, pleural fluid, cerebrospinal fluid (CSF), exudate from draining lesions, or biopsy specimens. Intact spherules are usually 20 to 80 micrometers in diameter, thick-walled, and filled with small (2 to 4 micrometers) endospores. Endospores released into tissues from ruptured spherules may be mistaken for nonbudding yeasts. Because culturingCoccidioidescan pose a severe biohazard to laboratory personnel, the laboratory should be notified of the suspected diagnosis. DNA probes can rapidly identify the fungus once growth occurs in the laboratory. Serologic testing for anticoccidioidal antibodies includes Enzyme immunoassay, which is very sensitive and is commonly used to diagnose coccidioidomycosis Immunodiffusion (to detect IgM or IgG antibodies) Complement fixation (to detect IgG antibodies) Titers≥1:4 in serum are consistent with current or recent infection, and high titers (≥1:32) signify an increased likelihood of extrapulmonary dissemination. Complement fixation titers can be used to estimate disease severity; high titers suggest more severe disease. However, patients who are immunocompromised may have low titers. Titers should decline during successful therapy. The presence of complement-fixing antibodies in CSF is diagnostic of coccidioidal meningitis and is important because CSF cultures are rarely positive. A urine antigen test may be useful for diagnosing coccidioidomycosis in patients who are immunocompromised with severe forms of the disease, including pneumonia and disseminated infection. Using a polymerase chain reaction (PCR) technique to test lower respiratory tract samples for DNA can provide a more rapid diagnosis. However, this test is not widely available. 