Infectious Diseases

Answer 2 Urine test. With its high sensitivity and specificity, an enzyme-linked immunosorbent assay (ELISA) test of the urine can detect Histoplasma antigen in up to 90% of patients with disseminated histoplasmosis.1 The organism can be cultured in sputum specimens in about 20% to 60% of cases, but the cultures can take between 3 and 6 weeks to become positive if Histoplasma is present. Occasionally, blood cultures also will be positive in patients with disseminated histoplasmosis, especially if the lysis centrifugation technique is used. A peripheral smear would not aid in the diagnosis of histoplasmosis. Although abnormalities would be seen on computed tomography of the chest, a microbiologic diagnosis would still be needed. REFERENCE 1. Mandell GL, Bennett JE, Dolin R. Principles and practice of infectious diseases. 6th ed. Philadelphia: Churchill Livingstone; 2005. Click here to return to the questions

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