Approach to the Diagnosis of Histoplasmosis, Blastomycosis and Coccidioidomycosis

Abstract

The consequences of failing to consider the diagnosis of an endemic fungal infection may be catastrophic. The diagnosis can be made most rapidly by microscopic examination of tissues or by antigen detection in body fluids. These methods are recommended in patients with evidence for acute pulmonary disease, in patients with findings that are concerning for progressive and/or disseminated infection, and in those who are ill enough to require hospitalization. Antibody detection is most sensitive when using enzyme-linked immunoassay methods. However, antibody assays may be falsely negative in immunocompromised patients or within 2 months following acute infection. Conversely, positive results may persist for several years, resulting in an incorrect diagnosis in patients with other conditions. Cross-reactions also occur among the endemic mycoses. Testing for antigen in serum and urine and antibodies in serum are recommended in all acute or severe cases. When a procedure such as bronchoscopy or lumbar puncture is performed, efforts must be made to maximize the yield of the samples obtained. Hence, casting a broad net with antibody testing, antigen testing, and special stains on diverse fluids and tissues is recommended.