From the Guidelines
The initial screening workup for suspected coccidioidomycosis should include a combination of diagnostic tests, such as direct visualization and culture of sputum, BAL, or other biopsy material, urine and serum antigen testing, and serology (serum antibody testing), as no single test is sufficient for diagnosis. This approach is recommended due to the limited sensitivity of microbiological culture or organism visualization, which can be improved by adding serum antibody testing and urine and serum antigen testing 1.
When evaluating patients with suspected coccidioidomycosis, particularly those who are immunocompromised, urinary and serum antigen testing is suggested to aid in establishing the diagnosis, as it can increase the overall diagnostic yield 1. Additionally, serological testing of blood is recommended in all patients with suspected coccidioidomycosis, with repeat quantitative serological testing approximately every 12 weeks during care to evaluate response to therapy 1.
The screening workup should also include:
- A chest radiograph to assess for pulmonary involvement, which may show infiltrates, nodules, cavities, or hilar lymphadenopathy 1
- Microscopic examination of clinical specimens with standard fungal stains for the presence of Coccidioides spp. 1
- A CSF sample should be obtained from all patients suspected of meningitis 1
- Additional testing, such as complete blood count and comprehensive metabolic panel, may be necessary to evaluate organ function and check for eosinophilia, which is common in coccidioidomycosis.
It is essential to tailor the workup based on the patient's symptoms, as coccidioidomycosis can present with varied manifestations ranging from mild respiratory illness to disseminated disease.
From the Research
Initial Screening Workup for Suspected Coccidioidomycosis
The initial screening workup for suspected coccidioidomycosis typically involves serologic tests to detect antibodies against Coccidioides immitis.
- Qualitative tests such as immunodiffusion, enzyme immunoassay, or latex particle agglutination can detect the major antibody responses, including coccidioidal IgM in early coccidioidomycosis and complement fixing (CF) IgG, which appears later and is more persistent 2, 3, 4.
- Quantitation of the level (titer) of coccidioidal IgG is useful in prognosis and diagnosis 2, 4.
- The preferable antigen for these tests is coccidioidin from the hyphal phase of Coccidioides immitis 2, 4.
- In addition to serologic tests, polymerase chain reaction (PCR) testing can be used to detect Coccidioides sp. in clinical specimens, particularly in respiratory specimens 5.
- PCR testing has been shown to have a sensitivity of 75% and a specificity of 99% compared to culture of respiratory specimens 5.
Special Considerations
- Immunocompromised patients may have a limited humoral responsiveness, making serologic testing less reliable 3.
- In such cases, combining the results of multiple serologic tests can increase the sensitivity of the serologic evaluation 3.
- It is essential to interpret serologic test results in the context of clinical presentation and other diagnostic findings 2, 3, 4.